1. Unit 5
ENERGY

2. Energy Kinetic Energy Potential Energy Energy of motion
Energy of position

3. Kinetic Energy (KE) Depends on mass and velocity
Inversely proportional
KE is a scalar quantity
Unit is the joule (J)

4. A 7. 00 kg bowling ball moves at 3. 00 m/s
A 7.00 kg bowling ball moves at 3.00 m/s. How much kinetic energy does the ball have?

5. How fast must a 2.45 g ping-pong ball move in order to have the same kinetic energy as the bowling ball?

6. Potential Energy (PE) Gravitational Potential Energy
Energy due to the object’s position relative to a zero level

8. Gravitational Potential Energy
Depends on mass, height, and acceleration due to gravity
Unit is the joule (J)

9. A spoon is raised 21. 0 cm above a table
A spoon is raised 21.0 cm above a table. If the spoon and its contents have a mass of 30.0 g, what is the gravitational potential energy associated with the spoon at that height relative to the surface of the table?

10. Potential Energy (PE) Elastic Potential Energy
Energy due to the object’s position when it is stretched or compressed

11. Elastic Potential Energy (PEe)

12. Elastic Potential Energy (PEe)
k is the spring constant
units of newtons divided by meters (N/m)
x is the distance compressed or stretched
usually the difference between unstretched and stretched lengths

14. A stuntman is attached to a bungee cord with an unstretched length of 15.0 m. He jumps off a bridge spanning a river from a height of 50.0 m. When he finally stops, the cord has a stretched length of 44.0 m. Assuming the spring constant of the bungee cord is 71.8 N/m, what is the elastic potential energy?

15. Work – Kinetic Energy Theorem
∆KE = KEf – KEi

16. A 65 kg crate is pushed along a horizontal surface by two students
A 65 kg crate is pushed along a horizontal surface by two students. After the crate is pushed a distance of 6.0 m, starting from rest, its speed is 4.5 m/s. Find the magnitude of the net force on the crate.