Chapter 13Section 3: Energy Standards Standards 3: Motion and Standard 4: Forces Demonstrate the relationships among work, power, and machines Investigate the Law of Conservation of Energy Objectives 1. Explain the term energy giving examples as well as relating energy to work 2. Define potential energy and give examples 3. Solve gravitational potential energy problems 4. Define kinetic energy in terms of the factors that affect it 5. Solve kinetic energy problems 6. Explain the term mechanical energy in terms of where it comes from 7. Explain how living things obtain energy Energy!!! We use all kinds of energy Energy is The capacity to do work! Whenever work is done energy is transformed/transferred! Types of energy: Chemical, mechanical, electrical, solar, wind, nuclear, ect! Energy is measured in… Joules!! (J) What else is measured in Joules? WORK!!! So work is a form of energy! Objective 1: Explain the term energy giving examples as well as relating energy to work POTENTIAL Energy!!! Energy of position! Stored energy Results from relative positions of objects in a system Two types Elastic potential – potential of a stretched band or spring Gravitational potential – stored energy that results from the gravitational attraction between objects GPE!! (PE) Depends on mass and height! Formula = ℎ What is g? Acceleration due to gravity = 9.8 m/s 2 Objective 2: Define potential energy and give examples Calculating!!! Gravitational potential energy problems only give Mass and height YOU MUST REMEMBER TO MULTIPLY BY g!!! Calculate the gravitational potential energy of the following: A 1200 kg car at the top of a hill that is 42 m high A 65 kg climber on top of Mount Everest (8800 m) A 0.52 kg bird flying at an altitude of 550 m Objective 3: Solve gravitational potential energy problems Kinetic Energy!!! The energy of motion! Results from the motion of objects Can come from the potential energy an object has Depends on two variables Mass Velocity Formula = 1 2 m 2 Which variable does KE depend on more? Why? Velocity because it is squared Objective 4: Define kinetic energy in terms of the factors that affect it Calculating!!! What is the kinetic energy of a 44 kg cheetah running at 31 m/s? What is the kinetic energy of 1500 kg car moving at 67 m/s What is the kinetic energy of an 2.4 kg apple that falls a distance of 3.4 m in 1.4 s? We must calculate velocity first!! Objective 5: Solve kinetic energy problems Mechanical Energy!!! What do you think mechanical energy is? Energy of a machine – but it isn’t!!! Mechanical energy is the SUM of the POTENTIAL ENERGY and KINETIC ENERGY in a system! Also known as the AMOUNT of WORK we can do as a result of PE an KE! Everything has energy even atoms! Atomic energy is sometimes called non mechanical energy Most all energy comes from some form of kinetic and potential energies! Objective 6: Explain the term mechanical energy in terms of where it comes from Where Does Energy Come From?! Where do living things get energy? From food (PLANTS) Plants get energy from the sun So ultimately all energy comes from the sun The sun gets energy from nuclear fusion reactions (non- mechanical energy) Small masses are converted into large amounts of energy! Energy can also be stored in magnetic and electric fields Light is a form of this type of energy Objective 7: Explain how living things obtain energy