Unit 4: Momentum and Energy

A 1-kg glider and a 2-kg glider both slide toward each other at 1 m/s on an air track. They collide and stick. The combined mass moves at

1/3 m/s

A 5-kg shark swimming at 1 m/s swallows an absent-minded 1-kg fish swimming toward it at 4 m/s. The speed of the shark after his meal is

1/6 m/s

The work you do when pushing a shopping cart twice as far while applying twice the force is

four times as much

Although perpetual motion is the natural order of things in the universe

no perpetual-motion device that multiplies energy exists.

A ball rolling down an incline has its maximum kinetic energy at

the bottom

A toy elevator is raised from the ground floor to the second floor in 20 seconds. The power needed using 1000 J of work, is

50 W

Danny Diver weighs 500 N and steps off a diving board 10 m above the water. Danny hits the water with kinetic energy of

5000 J

Two 5000-kg rail cars roll without friction (one at 1 m/s, the other at 2 m/s) toward each other on a level track. They collide, couple, and roll together with a combined momentum of

5000 kg m/s

The power required to exert 4-N force over 3 meters in 2 seconds is

6 W

Two identical particles move toward each other, one twice as fast as the other. Just before they collide, one has a kinetic energy of 25 J and the other 50 J. At this instant their total kinetic energy is

75 J

A 2-kg ball is held 4 m above the ground. Relative to the ground its potential energy is

80 J

Consider massive gliders that slide friction-free along a horizontal air track. Glider A has a mass of 1 kg, a speed of 1 m/s, and collides with Glider B that has a mass of 5 kg and is at rest. If they stick upon collision, their speed after collision will be

1/6 m/s

The mass of a ball moving at 3 m/s with a momentum of 48 kg m/s is

16 kg

The power expended doing 100 J of work in 50 s is

2 W

The speed of a 4-kg ball with a momentum of 12 kg m/s is

3 m/s

Which has greater kinetic energy?

a car of half the mass traveling at 60 km/hr

It is correct to say that impulse is equal to

a change in momentum

A machine that promises more energy output than input is

a fantasy

A car traveling along the highway brakes to a stop over a certain distance. More braking force is required if the car has

all of the above

A moving object has

all of these

A red car has a head-on collision with an approaching blue car with the same magnitude of momentum. A green car driving with the same momentum as the other cars collides with an enormously massive wall. Which of the three cars will experience the greatest impulse?

all the same

Whether a truck comes to a stop by crashing into a haystack or a brick wall, the impulse is

both the same

The bob of a simple pendulum has its maximum kinetic energy at the

bottom of its swing

If a Ping-Pong ball and a golf ball both move in the same direction with the same amount of kinetic energy, the speed of the Ping-Pong ball must be

more than the golf ball

An object has gravitational potential energy due to its

height

A large heavy truck and a small baby carriage roll down a hill. Neglecting friction, at the bottom of the hill, the baby carriage will likely have

less momentum

A melon is projected into the air with 100 J of kinetic energy in the presence of air resistance. When it returns to its initial level its kinetic energy is

less than 100 J

If an all-electric car has kinetic energy, then it also must have

momentum

If the speed of a motor scooter doubles, which of the following also doubles?

momentum

The work you do when pushing a shopping cart twice as far while applying the same force is

twice as much