Kinetic and Potential
Energy Conservation
Work
Power
Pendulum and Springs
100
As a student walks downhill at constant speed, what happens to his gravitational potential energy and kinetic energy
gravitational PE decreases and KE remains constant
100
A 1.47-newton baseball is dropped from a height of 10.0 meters and falls through the air to the ground. The kinetic energy of the ball is 12.0 joules the instant before the ball strikes the ground. What is the maximum amount of mechanical energy converted to internal energy?
2.7J
100
When 150 joules of work is done on a system by an external force of 15 newtons in 20. seconds, the total energy of that system increases by
150 J
100
Two construction cranes are used to lift identical 1200-kilogram loads of bricks the same vertical distance. The first crane lifts the bricks in 20. seconds and the second crane lifts the bricks in 40. seconds. Compared to the power developed by the first crane, the power developed by the second crane is
half as great
100
The diagram 
shows an ideal simple pendulum. As the pendulum swings from position A to position B, what happens to its total mechanical energy? [Neglect friction.]
stays the same.
200
What is the kinetic energy of a 55-kilogram skier traveling at 9.0 meters per second?
2.2 x 103 J
200
After a 65-newton weight has fallen freely from rest a vertical distance of 5.3 meters, the kinetic energy of the weight is
340 J
200
A block initially at rest on a horizontal, frictionless surface is accelerated by a constant horizontal force of 5.0 newtons. If 15 joules of work is done on the block by this force while accelerating it, the kinetic energy of the block increases by
15 J
200
A car engine supplies 2000 joules of energy during the 10. seconds it takes to accelerate the car along a horizontal surface. What is the average power developed by the car engine while it is accelerating?
200 W
200
A spring has an unstretched length of 0.40 meter. The spring is stretched to a length of 0.60 meter when a 10.-newton weight is hung motionless from one end. The spring constant of this spring is
50 N/m
300
Two objects, A and B, are held one meter above the horizontal ground. The mass of B is twice as great as the mass of A. If PE is the gravitational potential energy of A relative to the ground, then the gravitational potential energy of B relative to the ground is
2PE
300
A motor does 20. joules of work on a block, accelerating the block vertically upward. Neglecting friction, if the gravitational potential energy of the block increases by 15 joules, what happens to the kinetic energy?
KE decreases by 15 joules
300
A horizontal force of 20 newtons eastward causes a 10 kilogram box to have a displacement of 5 meters eastward. What is the total work done on the box by the 20-newton force?
100J
300
What is the rate at which work is done in lifting a 35-kilogram object vertically at a constant speed of 5.0 meters per second?
1700W
300
A spring stores 10. joules of elastic potential energy when it is compressed 0.20 meter. What is the spring constant of the spring?
500 N/m
400
Show the graphing relationship between the gravitational potential energy (GPE) of an object near the surface of Earth and its height above the surface of Earth.
400
A block slides across a rough, horizontal tabletop. As the block comes to rest, what type of energy increases?
Internal energy due to friction
400
A 15.0-kilogram mass is moving at 7.50 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 11.5 meters per second?
570J
400
The graph below represents the work done against gravity by a student as she walks up a flight of stairs at constant speed. Compared to the power generated by the student after 2.0 seconds, the power generated by the student after 4.0 seconds is
the same
400
A compressed spring in a toy is used to launch a 5.00-gram ball. If the ball leaves the toy with an initial horizontal speed of 5.00 meters per second, what is the minimum amount of potential energy stored in the compressed spring?
0.0625 J
500
What is the total amount of gravitational potential energy gained by the box?
279 J
500
A 25-gram paper cup falls from rest off the edge of a tabletop 0.90 meter above the floor. If the cup has 0.20 joule of kinetic energy when it hits the floor, what is the total amount of energy converted into internal (thermal) energy during the cup’s fall?
0.02 J
500
55 N of force are applied to slide the box up the ramp. What is the total amount work done?
308 Joules
500
Identify the physical quantity represented by the slope of the graph.
Power
500
A vertical spring has a spring constant of 100. Newtons per meter. When an object is attached to the bottom of the spring, the spring changes from its unstretched length of 0.50 meter to a length of 0.65 meter. What is the magnitude of the weight of the attached object?
15N