Physics Work & Energy test

A person on a roof throws one ball downward and an identical ball upward at the same speed. The ball thrown downward hits the ground with 100 J of kinetic energy. Ignoring air friction, with how much kinetic energy does the second ball hit the ground?

100 J

An arrow in a bow has 70 J of potential energy. Assuming no loss of energy to heat, how much kinetic energy will it have after it has been shot?

70 J

Compared to yesterday, you did 3 times the work in one-third the time. To do so, your power output must have been

9 times yesterday's ouput.

Which of the following is not an example of potential energy?

A car moving on a flat road.

The unit of work is the

Joule (J)

An acorn falls from a tree. Compare its kinetic energy K, to its potential energy U.

K increases, and U decreases.

King Kong falls from the top of the Empire State Building, through the air (air friction is present), to the ground below. How does his kinetic energy (K) just before striking the ground compare to his potential energy (U) at the top of the building?

K is less than U.

Two men, Joel and Jerry, push against a wall. Jerry stops after 10 min, while Joel is able to push for 5 min longer. Compare the work they do.

Neither of them do any work

Can work be done on a system if there is no motion?

No, because of the way work is defined.

A truck weighs twice as much as a car, and is moving at twice the speed of the car. Which statement is true about the truck's kinetic energy (K) compared to that of a car?

The truck has 8 times the K of the car.

Describe the energy of a car driving up a hill.

both kinetic and potential

A ball is thrown into the air with 100 J of kinetic energy, which is transformed to gravitational potential energy at the top of its trajectory. When it returns to its original level after encountering air resistance, its kinetic energy is

less than 100 J

Potential energy is the energy an object has because of its

location

An object that has kinetic energy must be

moving

As a pendulum swings back and forth

potential energy is transformed into kinetic energy. kinetic energy is transformed into potential energy. at the lowest part of its swing its energy is all kinetic. at the end points of its swing, its energy is all potential.

A job is done slowly, and an identical job is done quickly. Both jobs require the same amount of work but different amounts of

power.

The amount of potential energy possessed by an elevated object is equal to

the work done in lifting it.

If you lift two loads up one story, how much work do you do compared to lifting just one load up one story?

twice as much

Power is defined as the

work done on an object divided by the time taken to do the work

Energy is changed from one form to another with no net loss or gain.

Always true.

The unit of power is the

Watt (W)

In physics, work is defined as

force times distance

If Nellie Newton pushes an object with twice the force for twice the distance, she does

four times the work.