Name
Date
Energy
Conservation of Energy
Instructions: Do every problem using LEPA on a separate sheet of paper.
1. A 200 kilogram mass is lifted by a crane. It is lifted vertically 50 meters.
a. How much work is done? 98,000 J
b. If the mass is raised in 140 seconds, how much power is used? 700 W
2. A horizontal force of 5.0 newtons acts on a 3.0 kilogram mass over a distance of 6 meters
along a horizontal, frictionless surface. What is the change in kinetic energy of the mass
during its movement over the 6 meter distance? 30 J
3. A 15 kilogram cart at the foot of a hill 5 meters high. For the cart to reach the top of the
hill, what is the minimum kinetic energy of the cart before it goes up the hill? 735 J
4. A 50 kilogram rock rests on a cliff 100 meters high. The rock falls the 100 meters and
lands on a spring, which gets compressed a distance of 15 meters. What is the spring
constant of the spring? [2 equations] 435.56 N/m
5. During a lab experiment, a student compresses the spring in a pop-up toy and does 0.2
joule of work to it. If the mass of the toy is 0.01 kilogram, what is the maximum vertical
height that the toy can reach after the spring is released? 2.04 m
6. On a roller coaster, the top of the roller coaster is 20 meters higher than the bottom of the
roller coaster. A cart filled with physics students has a total mass of 500 kilograms.
What is the velocity at the bottom of the roller coaster assuming the cart starts from rest?
[2 equations] 19.8 m/s
7. A toy cart possessing 8 joules of kinetic energy traveling on a frictionless, horizontal
surface toward a horizontal spring. If the cart comes to rest after compressing the spring
a distance of 1.5 meter, what is the spring constant of the spring? 7.1 N/m
8. In the diagram below, an ideal pendulum released from position A swings freely to
position B.
As the pendulum swings from A to B, its total mechanical energy
a. decreases, then increases
c. increases, then decreases
b. increases, only
d. remains the same
9. A 12 kilogram mass is moving at 17.5 meters per second on a horizontal, frictionless
surface. What is the total work that must be done on the mass to increase its speed to 28
meters per second? 2866.5 J
10. A person weighing 650 newtons rides an elevator upward at an average speed of 2 meters
per second for 30 seconds. How much does this person’s gravitational potential energy
increase as a result of this ride? 39,000 J
11. A 670 Newton box is pushed up a ramp by an unknown force. The ramp has a length of
12 meters. How much gravitational potential energy did the box receive if it goes to a
height of 3.1 meters? 2077 J