Energy - AP Physics

Zero kinetic energy occurs when . . .

• a moving object falls to the Earth.
• speed reaches zero.
• speed increases.
• speed is constant but mass doubles.

A force does work on an object if a component of the force

• is parallel to the displacement of the object.
• parallel to the displacement of the object moves the object along a path that returns the object to its starting position.
• perpendicular to the displacement of the object moves the object along a path that returns the object to its starting position.
• is perpendicular to the displacement of the object.

A boy pushes on a parked car with a force of 200 N. The car does not move. How much work does the boy do on the car?

• Zero
• 200 N
• 200 J
• can't be determined

The law of conservation of energy states that . . .

• the energy of a system can disappear.
• energy cannot change form.
• it is impossible to make a perpetual motion machine.
• energy can neither be created nor destroyed.

What happens to the total amount of energy during an energy conversion?

• no friction.
• very little loss or gain of energy.
• energy loss due to heat.
• o loss or gain of energy.

A child moving at constant velocity carries a 2 N ice-cream cone 1 m across a level surface. What is the net work done on the ice-cream cone?

• 0.5 J
• 2 J
• 20 J
• 0 J

Describe the relationship between force and motion for work to be done.

• the applied force must be perpendicular to the direction of motion.
• the applied force must be opposite to the direction of motion.
• motion must be perpendicular to the direction of the applied force.
• the applied force must be the same as the direction of motion.

CALCULATIONS REQUIRED. The brakes on a car exert a frictional force of 6000N in getting the car to stop. If the work done by the brakes is 400000J in coming to a stop, how many meters did the car travel after the driver applied the brakes?

• 33 m
• 22 m
• 67 m
• 133 m

Car J moves twice as fast as car K, and car J has half the mass of car K. The kinetic energy of car J, compared to car K is

• 1 to 2.
• the same.
• 2 to 1.
• 4 to 1.

If you push twice as hard against a stationary brick wall, the amount of work you do

• remains constant but non-zero.
• remains constant at zero.
• doubles.
• is cut in half.