Download PS2, Energy Potential Energy, Kinetic Energy, and Conservation of

PS2, Energy
Potential Energy, Kinetic Energy, and Conservation of Energy
Standards:
2a. Students know how to calculate kinetic energy by using the formula KE 
1 2
mv .
2
2b. Students know how to calculate changes in gravitational potential energy near Earth by using the formula
(change in potential energy) PE  mgh (h is the change in the elevation).
2c. Students know how to solve problems involving conservation of energy in simple systems, such as falling

objects.
Equations:

Conservation of Energy:
1. Define energy.
1 2
1
mvi  mghi  mv 2f  mgh f
2
2

2. What are the units of energy? _______________________
3. Mechanical energy is the energy due to the ________________ or __________________ of something.
4. What are the two forms of mechanical energy?
a. ______________
b. ______________
5. Explain what the height is when you calculate an object’s gravitational potential energy.
6. Kinetic energy is energy of ____________________.
7. Is the following sentence true or false? If the speed of an object doubles, the kinetic energy of the object also
doubles.
8. Express the law of conservation of energy.
9. The figure above shows the energy of a swinging pendulum bob at different points along its path. If you
ignore friction, how does the energy of the bob at the highest points of its path compare to the energy at the
lowest point of its path?
PS2, Energy
10. What is the potential energy of a 7-kilogram potted plant that is on a 2 meter-high plant stand?
11. What is the kinetic energy of a 4-kilogram ball that is rolling at 3 meters per second?
12. What is the potential energy of a 3 kilogram-ball that is on the ground?
13. The potential energy of an apple is 6.00 joules. The apple is 3.00-meters high. What is the mass of the apple?
14. A ball is at rest on top of a hill with a potential energy of 500 J. The ball then rolls down to the bottom of the
hill. What is the ball’s kinetic energy at the bottom of the hill?
15. It is said that Galileo dropped objects off the Leaning Tower of Pisa to determine whether heavy or light
objects fall faster. If Galileo had dropped a 5.0-kg cannon ball to the ground from a height of 12 m, what would
have been the change in PE of the cannon ball?
16. Miss Stein climbs to the top of a 30 m high cliff and holds her hand out over the edge. She opens her hand
and drops a penny of mass 0.1 kg. What is the penny’s kinetic energy right before it hits the ground? What is
the penny’s velocity right before it hits the ground?
17. A 500 kg pig is standing at the top of a muddy hill on a rainy day. The hill is 100.0 m long with a height of 30
m. The pig slips and begins to slide down the hill. What is the pig’s speed at the bottom of the hill? Use the law of
conservation of energy.