3.1 UNDERSTANDING PRESSURE Define Pressure Formula of Pressure Pressure is force per unit area P = Pressure F = Force A = Contact Area The S.I. unit of pressure is: Pascal 1 Pa = 1 Nm-2 Other units: cmHg, atm Factors affecting Magnitude of the force: the magnitude of The larger the force, the higher the pressure. Pressure: Contact area: The larger the contact area, the lower the pressure. Applications involving High Pressure Increasing the pressure by reducing the area A sharp knife has a very small surface area on its cutting edge so that high pressure can be exerted to cut the meat. The studs on a football boot have only a small area of contact with the ground. The pressure under the studs is high enough for them to sink into the ground, which gives extra grip. Nails, needles and pins have very sharp ends with very small surface areas. When a force is applied to the head of a nail, the pressure will drive its sharp end into a piece of wood easily. The sole of an ice is fixed a narrow metal bar. The high pressure on surface of the ice so that the ice melts and allowing the ice skater to glide smoothly. Racing bicycles need very high air pressure inside the tyres, because the narrow tyres have a very small contact area with the road. The hard road surface can support the high pressure under the wheels. Application involving Low Pressure Reducing the pressure by increasing the area Skis have a large area to reduce the pressure on the snow so that they do not sink in too far. A tractor moving on soft ground has wide tires to reduce the pressure on the ground so that they will not sink into the ground. Example 3 The figure shows a 440 g wooden block. The wooden block will exert the maximum pressure when it is standing on the surface__________ What is the maximum pressure exerted by the wooden block? [Assume, g=10 Nkg-1] Example 4 A cylindrical pole of mass 120 kg has cross-sectional area of 200 cm2. Find the pressure exerted by the pole when it is standing vertically on the ground. [ g = 10 ms-2] Example 5 What is the pressure exerted by the 12kg box on the table? [Assume, g = 10 Nkg-1] Example 6 The surface of the floor can withstand pressure of not more than 20 kPa from the base of a 400 kg marble table. What is the suggested area for the base of the table to avoid breaking the floor? If the table has a base of 0.33 m2, what is the maximum load that can be placed on the tabletop? Exercise 1. Pa is equivalent to A. 1 N m2 C. 1 N m-2 B. 1 m N-2 D. 1 m N2 2. Figure shows a wooden block on a horizontal surface. The block will exert maximum pressure on a horizontal surface if it is resting on its face A. STUV B.TWXU C. WXYZ D. UVXY 3. An ice skater is able to glide smoothly across the surface of the ice because A. the low pressure between the edge of the metal bar and the ice melts B. the high pressure between the edge of the metal bar and the ice melts C. the low pressure between the edge of the metal bar and the ice freezes D. the high pressure between the edge of the metal bar and the ice freezes 4. A wooden block with the dimensions of 3 m x 4 m x 5 m is placed on a floor. If the mass of the metal block is 400 kg, what is the maximum pressure that can exerted by the metal block on the floor? A. 100 N m- 2 B. 200 N m -2 -2 C.333 N m D. 480 N m -2 E. 620 Nm -2 5. The mass of a boy is 60 kg. The pressure exerted by the boy on a floor is 2 x 10 4 Pa. What is the area of contact between the shoe’s base of the boy and the floor? A. 1.2 x 10 –2 m-2 B. 3.0 x 10-2 m-2 -2 -2 C. 4.5 x 10 m D. 6.0 x 10-2 m-2 -2 -2 E. 8.0 x 10 m 6. The figure shows a school bag. A wide shoulder pad of a heavy bag will reduce the pressure exerted on the shoulder of the person carrying the bag. Example 1 A block of metal of dimensions 0.5 m x 0.6 m x 1.0 m has a mass of 300 kg. Calculate the maximum pressure acting on the ground. Example 2 A student pressing a thumbtack into a piece of wood with a force of 20 N. The surface area of the head of the thumbtack is 1 cm2 and the cross-sectional area of the tip of the thumbtack is 0.01 cm2. Calculate: (i) the pressure exerted by the student’s thumb on the head of the thumbtack (ii) the pressure of the tip of the thumbtack on the wood. What is the function of x? A. to increase weight and to increase pressure B. to increase surface area and to decrease pressure C. to decrease weight and to decrease pressure D. to decrease surface area and to increase weight 1 the depth of sinking and the force involved. If the pin point has an area of 0.indicate and label: (i) the total area of contact between the tractor’s tyre and the soft ground (ii) the pressure exerted by the tractor on the soft ground (b) Based on the answers in (a)(i) and (a)(ii). (b) Explain why a car cannot moves on the soft ground although the mass of the car is less than the mass of the tractor? (c) What happens to the area of contact between the tractor’s tyre and the soft ground if the air pressure inside the tyres is decreased? 8. which of the following will produce maximum pressure on the floor? A. the pressure exerted by the tractor on the soft ground.1200kN B. If the area covered by a shoe is 0.40kN D. (d) A manufacturer of car wheels estimates that the area of a car wheel in contact with about the same as the area of a person’s shoe in contact with the ground.15 m2. 2N D. 4N B. Figure(a) (a) Based in the Diagrams (i) compare the contact area between the wheels (ii) compare the weight of the vehicle 1 and vehicle 2 (b) Which vehicle should the farmer use when driving across his fields when the ground is very soft? Give your reasons. (b) Explain why the difference of the observations occurs? (c) Relate your answers in (a) and (b) to deduce the concept in physics. (a) Calculate i. 12.5 m2. ABCDE B. (a) (b) Figure (a) Figure (b) (a) On Figure(a) and Figure(b) . (d) A man wearing snowshoes applies a pressure of 2500 Pa. what is the force acting on the wall? A. Figure(b) 2 . DEJI B Figure (a) Figure (b) (a) Observe the Figure (a) and Figure (b). 5N 13. which of the ways is more suitable on the muddy road? Explain the reason for your answer. The area of contact between a tractor’s tyre and the soft ground is 0. Observe the Figure (a) and Figure (b). Figure (a) and Figure (b) show two ways in which a gardener moves a wheelbarrow on a muddy road. If the wall has an area of 5m2. a) Compare the depth of sinking the pencil in the plasticine. The resultant force exerted by the wheel on the road surface is 500 N and the area of the wheel in contact with the road is 2 x 10-3 m2. find the minimum force for the pin to enter the board. The car has 4 tyres and a driver has 2 feet) (ii) Suggest why it might be a good idea to reduce the pressure of the air in car tyres if the car driven over soft sand. 6 kPa D. Figure (a) shows two different situations of a woman wearing a high heel shoes and then wearing a flat shoes. (c) The wheel of the wheelbarrow exerted pressure on the muddy road. c) Explain why a footballer likes Ronaldinho wearing a football boot has sharp studs? 11.800kN E. the conditions of the pencil. A farmer has two vehicles with the same mass and the same number of wheels. Explain your answer. CDIH D. What is the pressure acting at its base? A. BCHG C.02 mm2.1600kN C. The figure above shows a block of gold with uniform cross sectional area ABCDE placed on the surface of a floor. 12 kPa 14. (iv) Relate the pressure exerted on the balloon with the surface area (v) What happens to the pressure on the balloon if force exerted is increased? 16. (iii) State one modification that could be made to the wheelbarrow to reduce the pressure exerted on the road. The mass of a tractor is 4000 kg. 10.1000kN 15. Wind blows normally on a wall at a pressure of 200kPa. what is the mass of the man? 9. b) Relate the comparisons to deduce a concept in physics. ii. A car weighs 10 000 N and a driver weighs 500 N (i) Calculate the ratio pressure of car on ground: pressure of driver on ground. state two observations about the surface area contact. the pressure exerted must be greater than 5 x 107 Pa. the load and the conditions of the handwriting. 18 kPa C. (i) Which balloon will burst easily? (ii) Compare the pressure exerted on the balloon. (i) What does the word pressure mean? (ii) Calculate the pressure exerted on the surface of the muddy road. 1N C. 15 kPa B. Figure(a) shows two situations of a pencil with a load is placed on the top of the pencil sinking into a plasticine before and after it is sharpen Figure (b) shows two conditions handwriting by using a pencil before and after it is sharpens. Figure (b) shows two different situations of a skier without wearing snowshoes and then wearing snowshoes. For a pin to enter a wooden board. What is meant by pressure? Based on Diagrams. Diagrams show two balloons A and B exerted with the same force. If the block of gold can be placed in a stable state of any of its surface. (c) Name the physics concept involved. the total area of contact between the tractor’s tyre and the soft ground._________________________________________________________________________________________ 7. A cylinder has a mass of 12kg and a cross-sectional area of 200cm2. (iii) Compare the surface area of finger and needle which in contact with the balloon. The tractor has four tyres. A. 9 kPa E. Characteristic 1: The pressure in a liquid increases with depth.the area of its surface Characteristic 4: Pressure in liquid depends only on its vertical distance from the surface of the liquid. By giving g=10ms-2. Submarine is built with thick wall. Example 1 If the density of sea water is 1150 kgm-3. Characteristic 2: The pressure at any point of a liquid acts equally in all direction. what is the pressure of a) liquid M at point x b) liquid M and N at point y 3 . In order for the fluid to flow into the vein. Pressure at A = Pressure at B Example 4 Given that the density of mercury is 13600kgm-3.2 UNDERSTANDING PRESSURE IN LIQUIDS What is pressure in liquid? Pressure Caused by Liquid Pressure in liquid is due to the weight of the liquid acting on the surface of any objects in the liquid. Submarine is built with thick wall so as to withstand enormous pressure at greater depth. Calculate the pressure of mercury at a point 25cm from the mercury surface (g=10ms-2) Example 5 The figure shows a glass tube filled with 50cm height of liquid M and 30cm height of liquid N. The liquid solution is at a higher pressure so it has sufficient pressure to flow into the veins of the patient. The wall of the dam has to be thicker at the base. (Density of water = 1000kg m-3) Characteristic 3: For a given liquid. Find the pressure of water exerted on the fish. Applications of pressure in liquids Construction of Dam Dam holds water at high altitude. Example 2 The figure shows a cylinder containing liquid mercury. calculate the pressure below 40m of sea water due to the water alone. The wall of a dam is much thicker at the bottom than at the top because it must withstand the increased lateral pressure in depths of the water. .the size of the container. The densities of liquid M and N are 1000kgm-3 and 2500kgm-3 respectively. P = Pressure h = depth ρ = density of liquid g = Gravitational Field Strength Pressure in Liquid P = Pressure Patm = Atmospheric Pressure h = Depth ρ = Density of liquid g = Gravitational Field Strength Characteristics of Pressure in a liquid. A patient receiving intravenous drips of a certain fluid from a bottle.36 x 105 kg m-3 ] Example 3 Figure shows a fish in a lake.the shape of the container.3. Public Water Supply System The water tower is built at high place so that the water has sufficient pressure to flow to consumer’s house. the bottle must be placed at a height above the injection site. What is the pressure caused by the liquid mercury at the point P? [ Density of liquid mercury is 1. Characteristic 5: The pressure in a liquid is directly proportional to the density of the liquid. the pressure at a point within it varies only with the vertical depth of the point below the surface of the liquid. Pressure in liquid does not depends on . . What is the pressure due to the water at a depth of 5 m? [Assume g = 10 N kg–1. X. The container has three openings X. 80 cm D. Y 12. The figure shows a container filled with water. Q 170 C. The size of the container 4. 13. P. A solid ball is lowered into the water. Gravitational field strength B. The depth at which the pressure is measured B. From the figure. The density of the fluid D. The gravitational field strength C. B. 10.4 x 103 Pa. D. Water spurts out from the opening to different distances. C. 2. S 220 Table shows four identical containers are filled with same amount of different liquid. 4 . Water has a density of 1 000 kg m–1. 8. 2. R 190 D. Point R has a lower pressure than point P. Diagram shows a cylinder containing cooking oil. 24 cm B. a? A. Y. Liquid Q C. 30 cm C. which of the following statements is true? A. Point Q has a higher pressure than point P. 3. What is the density of the ball? A. PS = PT because S and T are at the same depth B. Which statement is correct? A. Z D Z. The density of substance X is 200 kg m-3.5 g cm-3 C. Y. Which of the following will not affect pressure in a fluid? A. Density of the liquid C. The pressure exerted by the cooking oil at the base is 2. and Z of the same size. All the points P. 4. are A X. Decreases C. (Density of water = 1000 kg m-3 ) Diagram shows water flows from the concrete tank to the house water tank. P 150 B. Diagram shows a concrete water tank filled with water. Which of the following factors will not affect the pressure in a liquid? A. Z B Z. in increasing order of how far water spurts out. PS < PT because the density of X is less than the density of Y D. of a column of water? 8. Liquid S 11.0 g cm-3 B. Volume of the liquid D. 18. and S have the same pressure. When the level of the water decreases. Increases B. The water level rises from the 30 cm3 mark to the 40 cm3 mark as shown in diagram. Liquid Density/ kgm-3 P 800 Q 900 R 1000 S 1100 Which container exerts the highest pressure at the bottom? A. In which liquid will substances X floats? Liquid Density (kgm-3) A. PS > PT because S is nearer to the bottom of the tube 9.] A 5 000 Pa B 10 000 Pa C 50 000 Pa D 100 000 Pa 5. what will happen to the distance.0 g cm-3 D.0 g cm-3 6. (a) (b) (c) (d) State a factor that affects the water pressure in the tank. Liquid R D. Point S has the lowest pressure. X. 7. Q. The density of cooking oil is 800 kg m-3. The openings. Y. Diagram shows liquid X and liquid Y in glass tubes. Liquid P B. 2400 cm Diagram shows water spurting out from a hole of a container at a distance of a. Depth of the liquid Which of the following graphs represents the relationship between the pressure. and the depth. A large tank is filled with water to a height of 10 m. The scale reading increases from 100 g to 180 g. PS = PT because S and T are at the same level C. What is the height of oil in the container? A. Remains constant The measuring cylinder containing some water stands on a scale pan. X C Y. Compare the water pressure at P and Q Calculate the water pressure at Q. h._________________________________________________________________________________________ Exercise 1. R. m. 16. J and K operate using pressure and receive water supply from the same tank located on a hill. (Water pressure = 1000 kg m-3) At 5. the water level in the water tank has dropped from P to Q. 17.] (a) What is meant by pressure? (b) State one factor which influences the height of the fountain (c) Calculate the pressure at K. (vi) The way to tabulate the data (vii) The way to analyse the data 5 .00 p. Diagram B shows a diver is diving into the swimming pool. Draw a water tank that can withstand high water pressure. compare the depth of the water in both containers. Given that the density of water is 1 000 kg m–3. Figure shows fountains J and K in a park. If a fish can withstand water pressure of 250 kPa. What is the factor that causes the water to flow from the concrete tank to the water tank in the house? ii.] 22. 15. (d) Compare the height of fountain J and K in the morning and in the afternoon. 19. (b) State one suitable hypothesis. it exerts pressure on the container. 14. density of sea water = 1 000 kg m–3. 18. i. Diagram A shows a diver is diving into the sea.. m.distance travelled by the water spurts out. (e) Another pipe similar to that for fountains J and K is connected to the water pipe at X. Hence make a conclusion regarding the relationship between the pressure and the depth of the water. Given that the density of mercury is 13 600 kg m–3. Diagram A and Diagram B show how water spurts out from its container when the valve is opened. (a) What is meant by pressure? (b) With reference to Diagram A and Diagram B. Write a formula to find the pressure of a liquid. calculate the water pressure acting on the diver at a depth of 10 m below the water surface. What will be the liquid pressure if the container is brought to the Moon’s surface where its acceleration due to gravity is that of the Earth? 21. (a) State one suitable inference. Predict the height of the fountain at X com pared to fountain J. The flow of water from the concrete tank to the house will stop at level P. calculate the pressure of mercury at a point 20 cm from the mercury surface. Relate the distance travelled by the water that spurts out to the depth of the water. meter ruler and others. Suggest two modifications that can be done to ensure the water flow continuously to the house water tank. what is the maximum depth the fish can go under the water surface? [g = 10 m s–2. describe an experiment framework to investigate the hypothesis stated in (b) (i) The aim of the experiment (ii) The variables in the experiment (iii) The list of apparatus and materials (iv) The arrangement of the apparatus (v) The procedure of the experiment. P is the water level in the water tank at 9. as shown in Figure below 20. (c) Explain the modifications that need to be made to the dam to enable it to store more water safely. (c) With the use of apparatus such as thistle funnel. State the meaning of each symbol used. They are at the same depth but the diver in Diagram A feel that his ear was sick. the rate at which water spurts out and the Diagram A Diagram B Based on the observation above and your knowledge of pressure in liquid. (b) Suggest two uses of the water in the dam. [g = 10 m s–2. iv. The base of a liquid container experiences a liquid pressure of 120 kPa. Diagram A Diagram B When a liquid is held in a container. Diagram A and Diagram B show the side view of two different models of a dam made from bricks and concrete.00 a. Describe how to control the manipulated variables and how to measure the responding variables. Diagram A Diagram B (a) Which model is preferable? Explain your answer. Explain why the supply stops? iii. The height. Conversion of Pa and cmHg Simple Barometer Pa = 0cmHg Pb = 26cmHg Pe = 76cmHg Pf = 84 cmHg For a given liquid. Atmospheric pressure acts equally in all directions. Therefore. When the air inside the hemisphere is pumped out so that it becomes a vacuum. The sucker is held in position by the high atmospheric pressure on the outside surface.3 GAS PRESSURE AND ATMOSPHERIC PRESSURE Gas pressure Atmospheric pressure Gas pressure is the force per unit area exerted by the gas molecules as they collide with the walls of their container. Instrument Used to Measure Atmospheric Pressure Simple Barometer Fortin Barometer Anaroid Barometer Atmospheric pressure is the pressure caused by the weight of the air above us.1 atm = 76cmHg Atmospheric Pressure and Altitude Atmospheric pressure decreases as the altitude increases. the air inside is forced out. 6 . The high atmospheric pressure outside exerts a great force on the can and causes it crashes. its pressure decreases._________________________________________________________________________________________ 3. Explanation The force caused by the atmospheric pressure acts on the surface of the cardboard is greater than the weight of the water in the glass. it will crash instantly. Explanation When the air inside the can is cooled. the pressure will be the same at same level. Pd = Pe = 76cmHg The difference of gas pressure at different level can be ignored if the difference of the height is not too large. Magdeburg Hemisphere Figure above shows a Magdeburg Hemisphere. At higher altitudes. Hence. Pc = Pd = 76cmHg h = height of mercury column ρ = density of mercury g = gravitational field strength Existence of Atmospheric Pressure The cardboard does not fall and the water remains in the glass even though it’s not supported by anything. Atmospheric pressure varies with the height of the object above sea level. Explanation The atmospheric pressure exerts a strong force on the outer surface of the hemisphere.Atmospheric Pressure at Sea Level = 1atm . h will remains unchanged when i) the glass tube is lifted up from the dish ii) the glass tube is lowered further into the dish iii) the diameter of the glass tube increases iv) the glass tube is tilted v) the quantity of mercury in the dish is increased Rubber Sucker When the sucker is pressed into place. the hemisphere cannot be separated even by a very great force. Crushing Can When a can filled with hot water is closed and is cooled down rapidly by pouring cold water on it. It decreases with the altitude or the height above sea level. the frequency of collisions of the molecules is lower. Therefore. the density and the temperature of the air are lower. Unit of The units of atmospheric pressure used in the SPM syllabus atmospheric include: pressure Pascal (Pa) centimetre/milimetre mercury (cmHg/mmHg) atmosphere (atm) metre water Notes: . holding the hemisphere tightly together. As a result. atmospheric pressure is lower. U-Tube A U-tube can be used to determine density Straw When a person suck through the straw. Density of water = 1000kg/m3] Pgas = Patm + Pliquid Pgas = Patm + hρg Pgas = Gas Pressure Patm = Atmospheric Pressure g = Gravitational Field Strength Example 5 Figure shows a U-tube filled with 2 liquids X and Y that do not mix. the pressure in the straw become low. The atmospheric pressure which is higher in magnitude. Vacuum Cleaner When a vacuum cleaner is switched on. forces the air and duct particles into the cleaner. [density of mercury = 13600 kgm-3] Example 2 Figure shows a simple barometer. they experience a change in momentum.6g/cm3.Syringe When the piston is pulled up. Find the equivalent value of this pressure in the unit of Pascal (Pa). Instruments used to measure gas pressure Manometer Bourdon Gauge Gas Pressure In A Capillary Tube Example 1 Given that the atmospheric pressure at Genting Highland is 72cmHg. Find the atmospheric pressure in the unit of a) cmHg b) Pa [Density of mercury = 13. Example 3 Figure shows a column of mercury in a glass tube. the pressure at any point of the same level is the same. Find the density of liquid X. what is the pressure of the gas inside the tube? Example 4 Figure shows the water levels in a water manometer used to measure the pressure of a gas supply. For different liquid with different density. The momentum change exerts a force on the wall. The atmospheric pressure outside which is higher will force the water into the straw and consequently into the mouth. the atmospheric pressure inside the cylinder will decrease.600 kgm-3] Manometer Difference of gas pressure at different level can be ignored. Force per unit area is the pressure exerted on the wall of the container. Some air is trapped in the glass tube. Given that the density of liquid Y is 1. Pessure on the surface of a liquid is equal to the pressure of the gas in contact. If the atmospheric pressure is 76cmHg. 7 . The atmospheric pressure outside pushes the liquid up into the syringe. causes the pressure inside the cleaner become low. For a given liquid (same liquid). Find the pressure of the gas in unit of i) cm water ii) Pa [Atmospheric Pressure = 1000cm Water. How gas pressure is produced? Gas molecules are at constant and random movements. it sucks out the air inside the cleaner. When the molecules collide with the wall of the container and bounce back. pressure will be different at the same level. 18 cm of water 10. (a) What is the value of h (b) What is the length of the vacuum space when the glass tube is (i) uplifted at height of 5 cm (ii) lowered further into the dish at a depth of 4 cm (c) If the density of mercury is 1.19 x 105 Pa B. A barometer as shown in the figure is carried to the top of a mountain from a beach. what is the pressure of the trapped air P? 6. How would the atmospheric pressure and the length ℓ vary? Atmospheric Pressure A B C D 2. 1. A bowl of hot soup covered with an airtight lid is left to cool as shown in the figure. Increases Decreases Increases Decreases Length. 2.600kg/m3] 3. 42 cm Hg B. 35 76 82 Example 7 The figure shows a mercury barometer is placed in a school laboratory where the atmospheric pressure is 75 cm Hg. Which of the following statements is true? A. determine (i) the atmospheric pressure in the units Pa (ii) the value of h if the mercury is replaced by water Example 8 The figure shows a barometer. which of the following is the correct pressure at points X. Hydrometer Liquid X is poured into arm Q of a U-tube that is filled with mercury. 82 35 76 D. Exercise 1._________________________________________________________________________________________ Example 6 Figure shows a capillary containing a column of mercury. 15 cm of water C. Fortin barometer B. the height of liquid X increases when the atmospheric pressure increases B. 76 82 35 C. Example 9 The figure shows a manometer containing mercury is connected to a gas supply. 1.14 x 105 Pa 8 . in Pa unit? A. The air molecules move faster than the water molecules D. What is the pressure of the gas X? [ Take atmospheric pressure = 76 cm Hg ] 4.36 x 104 kg m-3 and Atmospheric pressure = 76 cm Hg ] Example 10 If the atmospheric pressure is 76 cm Hg. 3. The figure shows a U-tube manometer used to measure the pressure of a gas supply. Altimeter Based on the figure of a simple mercury barometer. 17 cm of water D. Carburetor B. 8. 82 cm Hg D. the pressure at point T is higher than at point U C. The atmospheric pressure is greater than the air pressure in the bowl C.000Pa. Siphon C. The vacuum space is filled with a gas X. 1000 cm Hg E. Y and Z? X Y Z A. 7. Aneroid barometer D. 3 cm of water B. [Density of mercury = 13. 120 cm Hg Which of the following instruments is meant for measuring atmospheric pressure? A. 2. moves to the left B. What is the pressure of the gas trapped inside the J-tube. find the pressure of the gas trapped in the capillary tube. Calculate the pressure of the gas supply in the units (i) cm Hg (ii) Pa [ Density of mercury = 1. what is the pressure of the column in the glass tube? A. Fortin's barometer D. the test tube A. the density of water is higher than the density of liquid X Which of the following instruments is used for measuring gas pressure? A. If the atmospheric pressure is 100.90 x 105 Pa C. moves to the right C. Arm P is then filled with water until mercury in both arms are at the same level. 82 76 35 B. rises higher D. The airtight lid prevents the air molecules to decrease in size when the soup gets cold An inverted test tube with some air trapped in it is placed in a tank as shown in the figure. If the height of the mercury column is 24 cm and atmospheric pressure is 76 cm Hg. ℓ Increases Increases Decreases Decreases 9.36 x 104 kgm-3 and the density of water is 1 x 103 kgm-3.19 x 105 Pa D. When the piston is pushed inwards. point R and point S have the same pressure D. Why is it difficult to open the lid when the soup is cold? A. Bourdon gauge C.90 x 105 Pa E. Water vapour cannot escape and condenses on the lid B. 52 cm Hg C. sinks lower The figure shows a mercury column in a glass tube with trapped air in it. What is the difference in pressure between the gas supply and the atmospheric pressure? A. 5. The length of the glass tube is 100 cm. Describe changes on the height of the mercury column in both Diagrams. Give one reason to your answer.11. Diagram shows a set-up of apparatus for measuring atmospheric pressure. 13. Diagram shows an instrument for measuring atmospheric pressure. g = 10 Nkg1 ] (b) What will happen to the height of the mercury column if (i) the tube is slightly slanted? (ii) there is some air in the vacuum area? (c) Why is water not suitable to be used in a barometer? 18. [Atmospheric pressure = 76 cm Hg] 12.2 (a) Based on Diagram 5. A mercury manometer with one end attached to a gas supply measures a difference in the level of mercury of 32 cm. A mercury manometer as shown in figure is used to measure the pressure of certain gas in a metal container. A gas is pumped into the left arm of the mercury manometer. the atmospheric pressure = 75 cm of Hg. (a) Name the instrument. The figure shows a simple mercury barometer.36 x 104 kg m-3. Calculate the pressure of the trapped gas.8 N kg-1.1 and Diagram 5. what is the different height of the liquid X in the manometer ? 9 . Diagram 5. Diagram shows a manometer which can be used to measure gas pressure.2 (i) state similarities about the magnitude and the direction of pressures Magnitude : Directions: (ii) what is the total pressure at point W? (iii) state the relationship between pressure at W and the gas pressure (b) Based on the answers in (a)(ii) and (a)(iii). [Density of Mercury = 1. The figure shows a small amount of gas trapped in a J-tube.1 and Diagram 5.1 has less pressure than diagram 5. Figure below a simple barometer used in the laboratory to measure atmospheric pressure. Calculate the gas pressure. draw the levels of the liquid in both arms of the manometer if the pressure of the gas greater than the atmospheric pressure. (a) Name the liquid X.36 x 104 kg m-3.8 N kg-1.. (c) The gas supply is taken out. (b) The gas tap is opened so that gas can flow to the rubber tube into the manometer. write words equation that relate between the atmospheric pressure. What is the pressure of the gas? [Atm pressure = 76 cm Hg. Calculate the pressure of the gas supply in (a) cm Hg (b) pascal [Atm. (a) What is the value of the atmospheric pressure in cm Hg? (b) What is the pressure at point X in cm Hg? (c) If the density of the mercury is 1. The length of the vacuum column is 10 cm and the height of the mercury column is 76 cm.2 show two mercury manometers in a laboratory. The level of the mercury column is at ……. density of mercury = 1. g = 10 N kg-1] 16. atm pressure = 76 cm Hg) 14. Give the reason for your answer. mercury pressure and the gas pressure. (b) Why is mercury use in the instrument? (c) Calculate the atmospheric pressure in Nm2 . (ii) If the pressure of the gas = 100 cm of Hg .36 x 10 4 kg m . Pressure = 76 cm Hg. density of mercury = 1. calculate the atmospheric in pascal. The pressure on the left arm and the right arm is in equilibrium when the difference in height of mercury is 50 cm as shown in the diagram.36 x 104 and g is 9. (i) On Diagram.36 x 104 kg m-3] 15. (a) What is the atmospheric pressure in Nm-2? [Density of mercury = 13600 kgm-3. The gas supply in Diagram 5. (Density of mercury = 1. 20. 19. (a) What is the name for the instrument? (b) Determine the atmospheric pressure as measured by the instrument (i) in the cm Hg unit (ii) in the Pa unit (c) What is pressure at point P and Q? (d) State the change of length of the mercury column above the mercury surface (i) The tube is raised by 10cm (ii) The surrounding temperature increases (iii) The instrument is brought to the peak of a mountain (iv) Water vapor is brought to the vacuum region 17.3] (d) Diagram shows the instrument being placed in a vacuum chamber. g = 9. (b) the ratio of the surface area of the piston._________________________________________________________________________________________ 3. the piston of the master cylinder applies a pressure on the brake fluid. A hydraulic system must not contain any air bubbles in any position of its hydraulic fluid system. The friction between the brakes and brake shoes causes the vehicle to slow down and stop. When the handle is raised. What is the maximum weight of a car that can be lifted by the bigger piston? Application of Pascal’s Principle Hydraulic Jack 10 . Hydraulic System When the handle is pressed down. If a force of 250 N is applied to the small piston. F2. What is the value of X? Example 3 Figure shows a garage hydraulic lift with two pistons. This process is repeated until the load is sufficiently lifted up. This shows that the pressure applied to the plunger has been transmitted uniformly throughout the water.0 cm2. F1 is applied to the small piston resulting in a large output force. When the plunger is pushed in. The hydraulic fluid is forced into the large cylinder and hence pushes the piston moving upward. applied to the small piston. This pressure is transmitted uniformly to each cylinders at the wheel. cause the pistons at the wheels to push the brake shoes to press against the surface of the brake. A1 = 4. When the brake pedal is pressed. Example 1 In a hydraulic system the large piston has cross-sectional area A2 = 200 cm2 and the small piston has cross-sectional area A1 = 5 cm2. what is the force F. If the maximum force that can be applied on the smaller piston is 600 N. Hydraulic fluid from the buffer tank will be suck into the small cylinder. Hydraulic Brake F1 = Force exerted on the small piston A1 = area of the small piston F2 = Force exerted on the big piston A2 = area of the big piston A small input force. The magnitude of the force at the large piston depends on (a) the force. F1. on the large piston? Example 2 When incompressible fluid is moved through a hydraulic system.4 PASCAL’S PRINCIPLE Pascal's Principle Pascal's principle states that any change in pressure applied to an enclosed liquid will be transmitted to every point of the fluid without any change in magnitude. Hence A1d1 = A2d2 Hydraulic systems act as a force multiplier. Figure shows a 10 N weight balancing a X N weight placed on a bigger syringe. the volume through which the input system moved must be the same as the volume through which the output system. This will reduce the efficiency of the system as part of the applied force will be used up to compress the air bubbles. valve A is closed whereas valve B is opened. The bigger piston has a cross-sectional area. the water squirts equally from all the holes. The smaller piston has a cross-sectional area. They multiply the input force by a certain factor to gain a larger output force. The large piston can be lowered down by releasing the hydraulic fluid back to the buffer tank through the release valve. valve B will be closed while vale A will be opened. A2 = 240 cm2. what is the distance moved by the large piston. What is the pressure exerted on the piston? What is the force multiplier of this hydraulic jack? How much force is exerted on the larger piston? What is the principle been applied in (c)? The smaller piston is pushed down a distance of d1 = 100 cm and this has resulted in the larger piston moving up a bit. D. 40N E. (i) How much has larger piston moved? (ii) What is the assumption made in obtaining the answer in (e)(ii)? 9. the air bubbles will escape from the piston and cause the brake fluid to leak C. Calculate the force applied to the small cylinder. the air bubbles will expand when they are heated up and cause an explosion D. calculate the distance moved by the piston B. (a) What is the force which acts on piston A? (b) Calculate the pressure exerted on piston B. 55N C. Name the principle used in the hydraulic jack. 45N The figure shows a hydraulic pump. (d) If the piston A moves down by 6 cm. 5. 50N B.0 x 10 m2 respectively. (c) If the small piston is pushed down at a depth a 0. The cross-sectional area of piston A and B are 0. Braking system of a vehicle C. The cross-sectional areas of the main cylinder and the small cylinder are 5 x 10 . Diagram shows a hydraulic jack which can lift up a maximum mass of 1 metric tonne. Determine the magnitude of force F2 if A2 = 5m2 Give one reason why it is more suitable to use a liquid instead of air as the hydraulic fluid. Figure shows the structure of a simple hydraulic jack where a small force F1 is used to produce a bigger force F2.2 m2 respectively. 2000 N D. Exercise 1. Diagram shows a model of a hydraulic jack. Diagram shows a hydraulic brake system of a car. the lower the pressure. Manometer D. If the smaller piston is pushed with a force of 15 N. The cross sectional areas of smaller piston and larger piston are 20 cm2 and 60 cm2 respectively. Pressure of liquid acts in all direction. Hydraulic jack B. the pressure is transmitted throughout the liquid.4 m2 and 6. The pressure transmitted in a liquid can result in a bigger output force compared with input force A mechanic notices some air bubbles in the hydraulic brake fluid of a car. A force of 1000 N is applied to smaller piston. When a pressure is applied to a liquid in an enclosed container. C. 30N D. what will be the force experienced by the larger piston? A. 7. 1000 N C. the further the transmission. Compare the fluid pressure at S and T to the pressure at R.005 m2 and 0. Determine (a) The pressure transmitted in the hydraulic fluid. (a) State the physics’ principle involved (b) On Diagram show the direction of motions of the main cylinder and the small cylinder. A1 and A2 are the cross sectional areas of the pistons.08 m2 and 1. 11 . He recommends changing the brake fluid.1 m2 respectively. 8. what is the weight of the load that can be lifted? A. (a) (b) (c) (d) (e) 4. A force of 20 N is applied to the small piston.04 m.5m2. calculate the pressure exerted on piston R. Water bed Which of the following statements is not true? A. 5000 N 2. the air bubbles will increase in size and cause the brake fluid to be incompressible The figure shows a hydraulic jack. When pressure is transmitted in a liquid. Which of the following is not an application of Pascal's principle? A. 6. If the force applied is 10 N. If F1 = 5. (a) (b) (c) (d) (e) 3. 500 N B. (c) Calculate the mass of load Y which can be lifted by the piston B. (d) The brake pedal is pressed with a force of 15 N. This is because A.Example 4 The figure shows a basic hydraulic system has small and large pistons with cross-sectional area of 0. (b) The mass of the load. The force F the small piston R is able to support two loads which are placed on piston S and T. (c) State the relationship between the liquid pressure in the main cylinder and the small cylinder. B.0 N and A1 = 0. the air bubbles will easily be compressed by pressure and affects the transmission of pressure B. Example 5 Diagram shows a simple hydraulic press. a) The function of this machine is based on a principle in physics. iii. Pascal’s principle states that when pressure is applied to an enclosed fluid. The hydraulic jack in the figure shows that piston A and piston B are of cross-sectional area 5 cm2 and 100 cm2 respectively. b) Explain why a small force exerted by the boy can result in a much bigger force acting on the old newspaper. Figure shows a glass barrel fitted with a plunger. If a mass of 3 kg is placed on piston A. The figure on the right shows a hydraulic jack. what is the distance moved by piston Y 12. Diagram shows a machine controlled by a worker to dump soil. a large force is produced on piston Y. 14. (b) When the pedal is pressed. His feet will sink into the snow if the pressure exerted exceeds 500 Pa. Which of the above is not an application of Pascal’s principle? 16. handle and ability to reset the piston position easily of the hydraulic jack to enable it to lift mass of greater quantity 10. The machine consists of a hydraulic system with two pistons as shown in figure. Study the specifications of all the four types of liquid from the following aspects: i) Boiling point of the liquid ii) Specific heat capacity of liquid iii) Density of liquid iv) Rate of vaporation of liquid (d) A man of mass 60 kg walks on snow wearing snow shoes. type of liquid used. explain why the hydraulic system in this machine is known as a force multiplier. 11. 15.28 m2. The figure shows a hydraulic jack whereby a car of weight 8 000 N is placed on top of the larger piston. 13. You are required to determine the most suitable liquid that can be used as a hydraulic fluid in the hydraulic jack. The cross-sectional areas of the smaller piston and larger piston are 20 cm2 and 60 cm2 respectively. with different specifications. b) State one inference concerning pressure applied on the water by the plunger. (a) Name the parts which are labelled P and Q respectively. Diagram shows a simple hydraulic machine used for lifting heavy loads such as cars in a garage. X and Y of cross sectional area 0. material of the body. It consists of two pistons. A boy invented a machine to compress old newspaper. ii. 17. explain the modification that needs to be done to the: i. The figure shows the hydraulic braking system of a car. and N. The cross-sectional area of the small piston and the large piston are 0. what will happen to the pistons? (c) What will happen if air is mixed with the liquid in the hydraulic brake system? 12 . A hydraulic system helps to move the bucket containing soil. a) State your observation when the plunger is pushed towards the bulbous end.02 m2 and 0. respectively. When piston X is pressed down by applying a force of 15 N. Name the principle. Piston A has a smaller crosssectional area compared to piston B. (c) Diagram shows a hydraulic jack lifting the back portion of the car. L. size of the piston.2 m2 and 4 m2 respectively. If the smaller piston is pushed with a force of 15 N. The other end of the barrel is with holes of uniform size. (a) (b) (c) Calculate the pressure exerted on the liquid by piston X Calculate the maximum load that can be lifted by piston Y If piston X is depressed downwards by a distance of 21 cm._________________________________________________________________________________________ Using suitable physics concepts. K. what will be the force experienced by the larger piston? Table shows four type of liquid. what is the maximum weight that can be lifted by piston B? 18. (a) What is meant by pressure? (b) Using a concept of pressure in liquid. (i) What is the weight of the man? (ii) Calculate the minimum area of each snow shoe so that he will not sink into the snow. (a) What is the minimum force that must be applied to the small piston in order to lift the car? (b) What is the transmitted pressure? 19. the pressure will be transmitted with equal _____________________________ to all parts of the fluid. M. iv. The balloon rises when the buoyant force is less than its weight. its apparent weight is 2. In a liquid of lesser density. What is the upthrust experienced by the object. The hydrometer floats more in a liquid of higher density. In Sport and recreation. The weight of the balloon can be varied by controlling the quantity of the volume of the gas in the balloon. The buoyant force is equal to the apparent loss in weight. When its weight is equal to the buoyant force.5 ARCHIMEDES’ PRINCIPLE Archimedes Principle states that when a body is wholly or partially immersed in a fluid it experiences an upthrust equal to the weight of the fluid displaced. W = mg =ρobjectVobjectg A submarine applies the principle to enable it to floating and sinking. It is to ensure that a ship is loaded within safe limits. F = ρliquidVliquidg Weight. Principle of Floatation: Displaced volume of fluid = volume of the object that immerse in the fluid. When it is fully submerged in a liquid. balloon is filled with hot air which has a lower density than cold air. If weight of the object > upthrust *The object will sink into the fluid. The apparent weight loss of the object is due to buoyant force. The ballast tanks are special compartments in a submarine. when the ballast tank is filled with air so that the buoyant force is greater than the weight of the submarine. Example 1 The density and mass of a metal block are 3.0 kg respectively. 13 . the bigger the volume of the liquid displaced. when a ballast tanks are filled with water so that the buoyant force is less than the weight of submarine. A ship will be submerged deeper in fresh water because the density of fresh water is less than the sea water. Lead shots are placed in the bulb to ________in down and enable the hydrometer ________ vertically in the liquids. Moreover. W = mg =ρobjectVobjectg Applications of Archimedes Principle Submarine Density of Object < Density of water: Fully Immerse F=T+W F = Upthrust T = Tension of the string W = Weight Upthrust. Hot Air Balloon A hot-air balloon has a large volume of gas. Buoyant Buoyant force is an upward force exerted by a fluid on an force object immersed in it. Plimsoll line The density of sea water varies with location. Weather balloons use a light gas such as helium or hydrogen.2 N. Calculate the density of liquid if its volume displaced by the stone is 25 cm3 Example 3 An object of mass 5 kg floats on the surface water. Density of Object < Density of water: Partially Immerse Upthrust = Weight Upthrust. The bigger the volume of the object immersed. The submarine rises. F = ρliquidVliquidg Weight. It consists of a tube with a bulb at one end. When in water. Volume of liquid displaced = volume of the submerged part of the object. Buoyant force = actual weight – apparent weight = 25 – 15 = 10 N The object displaces a volume of water. the object experiences two forces: (a) The actual weight which acts downwards (b) The buoyant force which acts upwards. The weight of an object in air is its actual weight The weight measured when the object is immersed in a fluid is its apparent weight.3. Buoyant force = Weight object in air – weight in water Relate buoyant force with the actual weight and apparent weight Buoyant force makes thing seem to be lighter. The submarine submerges. If weight of the object = upthrust *The object is in balance and therefore floats on the surface of the fluid. Hydrometer A hydrometer is an instrument used to measure the density of liquids such as liquid in a battery. the Plimsoll line marked on the body of the ship acts as a guide. F = ρliquidVliquidg Weight. a greater volume of liquid must be displaced for the buoyant force to equal the weight and so the more the hydrometer is submerged. it remains stationary in the air. For this reason. [Density of water = 1000kg m-3 ] Example 2 A stone weights 2. a ship must displace more water to obtain sufficient buoyant force to support its weight. Equation for 1. W = mg =ρobjectVobjectg Density of Object > Density of water: Fully Immerse T+F=W F = Upthrust T = Tension of the string W = Weight Upthrust. Buoyant force = ρVg force 3. Find the upthrust that act on the metal block when it is fully immersed in water. a ship can float lower in the cold season as cold water has a higher density.2 ×103 kg m-3 and 5. Buoyant force = Weight of fluid displaced buoyant 2.5 N. An object is hung from a spring.2 m3 is hanging in a water tank as shown in the figure above. a) On figure above mark and label two vertical forces acting on the submarine. 9. what is the volume of the displaced sea water? A. When the ballast tank is empty. The beakers are identical.6 x 10 5 N B.5 m3 and its weight is 125 000 N. 64 m3 E.6 x 10 N D. 900 m3 3 C. b) State the relationship between the two forces. 3. 3. Diagram shows an object which has a weight of 0.0 N Diagram shows a ship full with load floating on the surface of sea water. Calculate a) The volume of the liquid displaced. The volume of the block is 2. the submarine floats at the surface of the sea with 3/4 of its volume below the surface of the sea. Justify your suggestions. The volume of the submarine is 240 m3. (d) Calculate the tension.4 m3 D. (b) State one factor that affects the pressure at a point below the surface of a liquid. density of water = 1 × 103 kg m-3] Exercise 1. [Density of water = 1000 kgm-3] (d) What is the volume of the object? 2.012 kg with uniform diameter and cross-sectional area 4 x 10-4 m2. 10. The Diagram shows a spring balance supporting a metal block in two situations.5 g cm -3. c) The buoyant force experienced by the object. and it is filled with sand so that it is made vertical in a beaker containing water.8 N kg-1) The figure shows a glass tube of mass 0.0 N C 1. 3.0 N B 0.25 N fully immersed in water. (g = 9. b) The mass of the liquid displaced. What is the different between readings of the compression balance in both Diagrams? Relate the answers in (b) and (d) Name the physics principle involved in these situations. The density of sea water is 1200 kg m-3. The density of the water in the lake is 1 010 kgm-3. 11. 7. 800 m3 B. What happens to the spring balance reading in Diagram when the metal block is immersed deeper into the water? 6. [Density of water = 1000 kg m-3] a) What is the buoyant force on the object? b) Determine the volume of the object. If the density of the sea water is 1250kgm-3. Find the tension of the string? [Density of the metal = 8 × 103 kg m-3. in the cable. 3. Its apparent weight is 0. Calculate the density of the solution if its volume displaced by the stone is 25 cm3.6 x 10 6 N 7 C. a) b) c) d) e) f) g) 5. [Density of water is 1000 kg m-3] Determine (a) The upthrust (b) The mass of sand in the glass tube. 4. When it is fully submerged in a solution.If the water displaced by the ship is 350 m3._________________________________________________________________________________________ Example 4 What is the buoyant force acting on the nut when immersed in water? 8. its apparent weight is 2.6 x 10 8 N An object of density 20 g cm -3 and mass 400 g is immersed in a liquid of density 1. (c) Calculate the weight of the water displaced by the block. 640 m A block of wood 10-3 m3 is half immersed in water. Diagram shows a block of concrete being lowered to the bottoms of a lake. what is the buoyant force acted on the ship? [Density of se water = 1030 kgm-3] A. T. What is the meaning of weight? What is the difference between the spring balance readings in both Diagrams? Name the force that is represented by the reading. 3.22 N. 14 . (a) What is the buoyant force on the object in water? (b) What is the weight of water displaced by the object? (c) Determine the volume of water displaced by the object. A stone weight 2.2 N. A ship of mass 80000kg floats on the sea surface. what is the weight of the block of the wooden air? A0N D 5. 6. c) Calculate the magnitude of one of the two forces d) Name the principle used e) The captain of the submarine observed that the submarine is not strong enough to dive safely to the bottom of the sea. Suggest modifications that can be made to the submarine to make it safer. The metal blocks are identical. If the density of water is 1000 kg m-3 and the acceleration due to gravity is 10 kg-1. Figure below shows the cross-section of a submarine.5 N E 10. (a) State the SI unit for pressure. Example 5 A block that has volume of 0. The compression balance in the Diagram show the readings of the weight of an empty beaker and the weight of a beaker filled with water respectively.5 N. 15. Based on the situation in Diagrams. The density of sea water and river water is 1025 kg m-3 and 1000 kg m-3 respectively. f) Name the physics principle that explains the situation above. compared to length in water. d) Based on the answer. ropes and loads that could be used for the purpose. name the physics concept involve. c) Describe the position of the boxes in the liquid. b) Compare the volume of water displaced by the boat in the sea and in the river. Explain your answer. you are assigned to investigate the characteristics of set balloons. (a) Name the principle above. Diagrams show two solid spheres A and B with different density place in the water. mark the level of water when the boat enter the river Mouth. (a) (b) What is meant by density? Based on Diagram. (i) Calculate the resultant force of the balloon (ii) Calculate the initial acceleration of the balloon (iii) What is your assumption in your calculation in c(ii)? (d) Table shows the characteristics of four sets. Explain your answer.12. moored with a load at the Book Festival. (a) What is the meaning of buoyant force? (b) Explain why the balloon and the load float? (c) If the mooring rope cut off. 13. Type of gas filled and Maximum Tension allowed Set Mass of loads /kg density /N A Helium (0. c) Compare the density of sea water and river water. the balloons will rise up. A.25 kg/m3) 5 100 As a supervisor. C and D of balloons. A principle states that: When a body is immersed wholly or partially in a fluid. a) State similarities about the volume and the net force of the boxes. Diagram show a boat made from steel floating at the sea. The mass of the boat is 7500 kg. The balloon and the load float at a certain height and the buoyant force acting on the balloon is 250 N. Diagram shows a hot air balloon floating stationary in the air. Diagram shows three boxes with different density at stationary state.17 kg m-3) 5 300 B Hydrogen (0. dried and then placed in oil. A fisherman finds that his boat is at different levels in the sea and in the river. the buoyant forces acting on the body is equal to the weight of the fluid it displaces. Base on the table. Diagram shows a freely floating hydrometer in water. although the boat carries the same load. Based on the Diagram 15 . g) A submarine can sail on the sea surface and under the sea by using the principle stated in (f). e) Deduce relationship between weight of the boat and the weight of the water displaced. Diagram shows the boxes float when placed in a liquid.17 kg m-3) 20 300 D Nitrogen (1. relate the weight of water displaced and upthrust (c) Name the physics principle involved (d) State one application of physics principle in 14. compare the density of sphere A and sphere B ii. relate the weight of sphere and the weight of water displaced v. i. (b) Mark on Diagram the direction of the two forces acting on the hydrometer. Predict the length of the hydrometer that is submerged in oil. ropes and loads. B . Give a reason for your answer. compare the weight of water displaced by sphere A and sphere B iv. The mass of the balloon is 5 kg. (c) The hydrometer is removed from water. a) Compare the level of the boat in the sea water and in the river water.How a submarine on the surface of the sea can submerge? 16. compare the weight of sphere A and sphere B iii. b) What will happen to the air balloon if the load is dropped? Explain your answer. 17. a) State the relationship between the weight of air balloon and the upthrust. b) What is the buoyant force acts on the boat? c) In the Diagram below. b) Compare the weight of the boxes in ascending order. d) Relate the volume of water displaced to the density of water. a) State one function of plimsoll line.09 kg/m3) 20 250 C Helium (0. 18. Diagram shows a gas balloon. a) material used b) plimsoll line c) shape and size of the barge 22. B. [Density of water = 1 000 kg m–3] 24. A furniture factory manager plans to manufacture a table that exerts the least pressure on a soft flooring. prove that your results are in accordance with the Archimedes’ principle.4 N B 3.] A 2. Relating the weight lost and the density._________________________________________________________________________________________ (i) Explain the suitable characteristics of the balloons. Diagram (b) and Diagram (c). compare the spring balance reading. Diagram shows a barge used to transport goods from fresh water port to the ship anchored away from the seaside. [Density of water = 1. i) State the change to the length of the glass tube immersed. Diagram (a). deduce a relevant physics concept. immersed in water and cooking oil respectively. You can emphasise on the following aspects in your modification. d) The glass tube is then placed in a beaker containing alcohol.] a) The length of the glass tube immersed in water is 6. ropes and loads so that it can be used (ii) Decide which set is most suitable to be used at the festival. Bunsen burner 27. Based on the spring balance readings. (iii) Explain why the others set is not suitable 19.6 × 103 kg m–3 and 1 000 kg m–3 respectively. ii) Explain your answer in (d)(i). describe your observations of i) the volume of the bubble.0 g cm–3. c) Calculate the mass of sand in the glass tube. C. D. Object P is floating on the water surface whereas object Q is hung from a rope and immersed in the water. given that the density of the cube is 8 × 103 kg m–3 and that of mercury and water are 13. calculate a) the volume water displaced b) the mass of the load c) the density of the load. Buoyant force is acting on both of the objects. c) Name the physics principle that explains the above situations. Which of the following is not an application of Archimedes’ principle? A. the weight loss of the rock and the density of the water and the cooking oil. d) As a gas bubble rises from the bottom of a lake. 26. Explain why the copper block sink in water but the bowl shape copper sheet floats on water. Which of the following is true about objects P and Q? A.6 N C6N D 18 N 25.0 g with uniform diameter and crosssectional area 3. 20. b) Without referring to the Archimedes’ principle. 28. What is the buoyant force acting on the block if it has a density of 5 × 103 kg m–3? [Water density = 1 000 kg m–3. Calculate the height of the cube in the water layer and in the mercury layer.0 cm. ii) the density of the gas in the bubble iii) acceleration of the gas bubble 16 . Hot-air balloon D. Submarine C. 23. The reading of the spring balance for each situation is as shown in Diagram e) State one application of the apparatus under discussion. Then. The glass tube is filled with sand to keep it floating upright in a beaker containing water. Diagram shows a copper block and a bowl shape copper sheet of same mass. deduce a formula for the buoyant force acting on the cube. The equation “Weight = Buoyant force” can be applied to both objects. which is completely submerged in a fluid. Using suitable physics concepts. shown in the diagram. The buoyant force acting upwards on object Q is equal to the tension of the rope. A 3 kg block is floating in water with of its volume in the air. The figure shows a load suspended in air and then immersed into water. c) A metal cube with sides 10 cm long is submerged between water and mercury. a) State Archimedes’ principle.0 cm2. move faster and safe in fresh and salt water. Diagram (b) and Diagram (c) show a rock hung on a spring balance in air. Which of the following designs should he consider for the shape of the base of the legs of the table? a) What is meant by weight? b) Using Diagram (a). There are two forces acting on object P and on object Q respectively. explain the required modification needed in designing a carry more and heavier goods. It is observed that the glass tube still floats vertically. Hydrometer B. The figure shows a glass tube of mass 12. 21. Find the i) volume of water displaced ii) weight of water displaced b) Write an equation in words to relate the forces acting on the glass tube with sand in it. Pressure at A > Pressure at B > Pressure at C. The higher atmospheric pressure forces the petrol to go up to the jet and is ejected to form a spray. 3. the air flows at a high velocity through a nozzle. Experiment 3 Pressure at B becomes lowest because the speed of the water is the highest. It works by regulating the quantity of petrol and air that enters the engine. The faster the movement of air will cause the lower the pressure between the balls. Bunsen Burner When the burner is connected to a gas supply. The ping-pong ball will be pushed closer to each other if there is higher atmospheric pressure which acts on them. called lift. This phenomenon is caused by low pressure above the ball. C or D the pressure of water is very low? 17 . its water pressure is the lowest. Activity to show Bernoulli’s Principle When the air is blown in the surface of a piece of a paper as shown. The difference between the pressures at the top and underside of the wing causes a net upward force. Application of Bernoulli’s Principle Aerofoil When a wing in the form of an aerofoil moves in air.6 BERNOULLI’S PRINCIPLE Bernoulli’s Principle Bernoulli’s principle states that when the velocity of a fluid is high. The mixture of gas and air enables the gas to burn completely to produce a clean. which controls the quantity of air. The higher pressure of the atmospheric air acts on the surface of the liquid insecticide causing it to rise up the metal tube. The outside air. the balls will A remain stationary B move closely to each other C move far apart to each other The figure shows the flow a liquid through a Bernoulli tube. The bottom of the ball has the higher atmospheric pressure which can hold the ball from falling down. When the air is blown harder through the straw.3. the pressure is high. The insecticide leaves the top of the metal tube through the nozzle as a fine spray. it is observed that the paper moves up. The figure shows water flows through a Venturi tubes from point P to point Q. The air flows past a choke valve. 2. The flow of air below the wing is slower resulting in a region of higher pressure. the air pressure on the surface of the paper will decrease. is drawn in and mixes with the gas. So the paper is pushed up by the higher atmospheric pressure which acts at the bottom of the paper. In this case. The figure shows two polystyrene spheres are hung by a string respectively. the flow of air over the top travels faster and creates a region of low pressure. the pressure is low and when the velocity is low. The smallest pressure of the liquid is at point…… When the air is blown harder through the straw as shown. The filter funnel is inverted and a pingpong ball is held below it. into a narrow section of the carburetor where the air velocity increases. Water flows from high pressure region to low region. it is observed that the ball is not falling down. In accordance to Bernoulli’s principle. the high velocity of the air in the narrow section creates a region of low pressure. Exercise 1. Experiment 2 The velocity of water is highest when it is flowing through the narrowest part of the horizontal glass tube. In which vertical tubes A. creating a region of low pressure. This happened because the air moved at a very high velocity on the surface of the paper. and smokeless flame Carburetor Carburetor is a device which controls the speed of a car engine. which is at atmospheric pressure. the gas flows at high velocity through a narrow passage in the burner. So the ping-pong balls get closer. Insect Spray When the plunger is pushed in. Experiment 1 The height of the water column shows the magnitude of the water pressure. When the air blows harder as shown in the diagram. which helps the plane to takeoff. Hence. The flow of air at high velocity creates a region of low pressure above the metal tube. hot. B. The two pingpong balls will move closely to each other. 6. 18 . and M (b) Mark the water levels in tubes P. (a) (b) (c) (d) (e) When the piston is pushed inwards. Archimedes’ principle D. Explain the principle. Q and R as shown in figure. Y and Z will the same The figure shows water rising up the tubes X. 8. 9. Z will the highest D. principle of conservation of momentum 11. and R. A horizontal tube AB with both ends closed with rubber stoppers is fixed with three vertical tubes P. Bernoulli’s principle The curved path taken by the ball is due to A. Which principle explains the figure? A Pascal’s principle B Bernoulli’s principle C Archimedes’ principle 12. (a) Compare the velocity of air at K. Q and R has the lowest pressure? Explain your answer in (c). Principle of conservation of momentum B. According to Pascal’s Principle. equilibrium of forces B. 10. When the air is blown. Y and Z? A. A ball which is thrown forward in a spin moves in a curve. the above system produces a water spray. The figure shows an arrangement of apparatus which is used to show the Bernoulli’s Principle. The uplift force is higher than the weight of object B. (d) Name the principle used. Q. Water of density 1 000 kgm-3 is poured into tube P until water reaches level W. 5. Water level in Z < Water level in Y < Water level in X D. The resultant force in direction of the motion of the object is zero C.Y and Z if the air is blown. Water level in X < Water level in Y < Water level in Z B. Q and R. The air pressure at Q is higher than that at P C. 15. Y will the highest C. Explain briefly how the insecticide can be sprayed out of the spray. The figure shows a ping-pong ball that does not fall when the water flows. Water level in X < Water level in Z < Water level in Y C. the level of water in tube A. Archimedes’ principle D. (c) Compare the pressure in tubes P. Diagram shows an insecticide sprayer. The motion of the ball can be explained by A. B. The tube is inverted into a basin of water. Water level in Y < Water level in Z < Water level in X The figure shows the wing of an aeroplane which is moving with a uniform acceleration in the direction shown by the arrow. L. Diagram shows an experiment._________________________________________________________________________________________ 4. Which of the following is true? A. Principle of conservation of energy C. Bernoulli’s principle C. Which of the following is true regarding the water level in tube X. X. The pressure in region P is higher than in region Q D. Which of the following is based on Bernoulli’s Principle? A Syringe B Drinking straw C Bunsen burner The figure shows a water spray that is produced when the air flows through the jet. The velocity of air in region P is higher than in region Q. 14. X will the highest B. The velocity of air at Q is higher than that at P The figure shows a motion a ball when it is kicked by a player. as shown in the figure. The air flows in the tube from A to B. Which of the following is true? A. Which of the following instruments is not based on Bernoulli’s principle? A Filter pump B Car carburettor C Rubber plunger D Wing of aeroplane 13. 7. what happens to the pressure at P? Explain your answer in (a) Which of the following areas P. mark with a ‘P’. ii. Which of the following diagram shows the correct level of water in tube T. U. the possible water levels of tube Q and tube R. calculate the pressure caused by water column at point X.(a) What are the heights of water levels for tube Q and tube R respectively? (b) By neglecting atmospheric pressure. i. Diagram shows a Bernoulli’s tube.” Using a suitable physics concept. (f) “It is dangerous for a child to stand near a fast moving train. calculate the force acted by the column of water in tube P. (C) (D) 17. Mark on the figure above. (e) Name the principle involved. Figure 6 (b) shows what happens when there is no air blown through the straw and when air is blown through the straw. iii. State the principle which relates velocity and pressure of water along the horizontal tube. Water flows uniformly from end A to end B of the tube and it is found that the water level of tube and it is found that the water level of tube P is at Z. Give reasons for your answer (e) The apparatus is modified so that the middle part of the horizontal tube becomes narrower as shown in figure. 16. the possible water levels for tube Q and tube R. (c) If the cross-sectional area of tube P is 4 x 10-5 m2. Compare the velocity of water at E and F. (d) Based on your answers. relate the speed of the air to the pressure of the air. to indicate the position where the air pressure is low. (d) If the rubber stoppers at both ends of tube AB are taken away so that water can flow uniformly from end A to end B. Mark on the figure above. Air is blown from left to right. explain the statement. V and W? (A) (a) Describe the observations in Figures (b) Compare the speed of air between the two ping pong balls (c) In Figure. then water at tube P rises until level Y as shown in figure. Figure 6 (a) shows what happen when a freely hanging ping pong ball is placed near a tap with no running water and a tap with running water. (B) 19 .