1. Types of Energy March 1, 2016 Chapter 4.1

2. Meme Moment

3. Sadly...

4. Review from 6 th Grade! 7 th grade chapter 4 = 6 th grade chapter 5 Covers: Types of energy o Not just “ways to make electricity” What energy does How energy is transferred

6. We are all stardust. Energy Matter Gray area Made in stars Ideas E=mc 2 Current topic

7. Definitions Energy: the ability to do work or cause change. Measured in joules (J). o 1 J = 1 kg· m 2 /s 2 o Energy never disappears – it just changes form Work: Force exerted on an object that causes it to move. “The transfer of energy.” o Not the same thing as a job! Power: the rate at which work is done. The rate at which energy is transformed. Measured in J/s = watts (W)

8. Types of Energy

9. Mechanical Energy Mechanical energy: energy associated with an object’s motion, position, and shape. o An object’s combined kinetic energy and potential energy ME = KE + PE Kinetic energy: energy due to an object’s motion Potential energy: energy that is stored. Energy from position or internal energy such as chemical bonds o Energy that an object might have if something changes.

10. Kinetic Energy KE = ½ mass velocity 2 Note the square Why is it OK to use speed and velocity interchangeably in this equation?

11. Practice! A dog has a mass of 20 kg and a speed of 3 m/s. What is its kinetic energy?

12. Potential Energy Different types of potential energy, such as gravitational potential energy, elastic potential energy, and chemical energy o Different formulas for each type of PE In mechanical energy, it has to be related to motion, position, or shape, so PE is usually gravitational or elastic

13. Potential Energy Elastic PE: comes from an object being stretched or compressed, like a spring Gravitational PE: comes from an object’s height If it falls from up high, it will accelerate more, which means it will have a bigger velocity, which means it will be turned into more kinetic energy Gravitational potential energy = weight height

14. Practice! A rock climber weighs 600 N and is 5 m up a cliff. What is her gravitational potential energy ?

15. Practice! A diver has a potential energy of 1400 J and kinetic energy of 350 J. What is the mechanical energy ? At one point in the same dive, the same diver has a potential energy of 1000 J. What is the kinetic energy ?