Physics Exam Chapter 7 Multiple Choice

Kinetic energy is defined to be one-half the

mass times the speed squared

What property is conserved of a ball as it falls freely in a vacuum?

mechanical energy

Assume that two cars have the same kinetic energy, but that the red car has twice the mass of the blue car. We then know that the speed of the red car is _______ as the blue car.

one-fourth as much

A 0.5-kg air-hockey puck is initially at rest. What will its kinetic energy be after a net force of 0.6 N acts on it for a distance of 2 m?

1.2 J

What is the gravitational potential energy of a ball with a weight of 50 N when it is sitting on a shelf 2 m above the floor?

100 J

A 1200-kg frictionless roller coaster starts from rest at a height of 20 m. What is its kinetic energy when it goes over a hill that is 10 m high?

120,000 J

A woman with a mass of 60 kg climbs a set of stairs that are 3 m high. How much gravitational potential energy does she gain?

1800 J

What is the kinetic energy of an 80-kg sprinter running at 9 m/s?

3240 J

How much work does a 60-kg person do against gravity in walking up a trail that gains 720 m in elevation?

432,000 J

If a sports car with a mass of 1000 kg travels down the road with a speed of 30 m/s, its kinetic energy is

450,000 J

A man with a mass of 70 kg falls 10 m. How much gravitational potential energy does he lose?

7000 J

A toy car has a kinetic energy of 12 J. What is its kinetic energy after a frictional force of 0.6 N has acted on it for 5 m?

9 J

Three identical stones are thrown with the same initial speed from the top of a cliff into the river below. Stone 1 is launched straight upward; Stone 2 is launched horizontally; and Stone 3, directly downward. Just before entering the river, which stone has the greatest speed?

A tie; all three reach the river with the same final speed

An object has a velocity toward the south. If a force directed toward the south acts on the object, it will initially cause the kinetic energy of the object to ________.

increase

Which has the greater kinetic energy, an 18-wheeler parked at the curb or a Volkswagen rolling down a hill?

Volkswagen

Under what conditions is the kinetic energy conserved in a collision?

When the collision is totally elastic

If a sports car with a mass of 1000 kg travels down the road with a speed of 20 m/s, its kinetic energy is 200,000 measured in

kg ∙ m²/s²

Two objects have different masses but the same kinetic energies. If you stop them with the same retarding force, which one will stop in the shorter distance?

both stop in the same distance

the kinetic energy of an object moving in a circle at a constant speed is

constant

An object has a velocity toward the south. If a force directed toward the north acts on the object, it will initially cause the kinetic energy of the object to _________.

decrease

Assume that two cars have the same mass, but that the red car has twice the speed of the blue car. We then know that the red car has _______ kinetic energy as the blue car.

four times as much

A bowler lifts a bowling ball from the floor and places it on a rack. If you know that weight of the ball, what else must you know in order to calculate the work she does on the ball?

the height of the rack

Assume that a red car has a mass of 1000 kg and a white car has a mass of 2000 kg. If the red car has twice the velocity of the white car,

the red car's momentum is twice as big.

Which has the greater kinetic energy, a heavy truck at rest or a moving roller skate

the roller skate

Assume that a red car has a mass of 1000 kg and a white car has a mass of 2000 kg. If both cars are traveling at the same velocity,

the white car's kinetic energy is twice as big.

An elephant, an ant, and a professor jump from a lecture table. Assuming no frictional losses, what could be said just before they hit the floor?

they all have the same speed