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Exam 3: Momentum and Energy

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Question 21

Multiple Choice

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A 2-kg mass weighs 20 N and is held 4 m above the ground. Its potential energy relative to the ground is

A) 8 J.
B) 20 J.
C) 60 J.
D) 80 J.
E) none of the above

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Question 22

Multiple Choice

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A 5000-kg freight car crashes into a 10,000-kg freight car at rest. They couple upon collision and move with a speed of 2 m/s. What was the initial speed of the 5000-kg freight car?

A) 4 m/s
B) 5 m/s
C) 6 m/s
D) 8 m/s
E) none of the above

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Question 23

Multiple Choice

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Suppose a miracle car has a 100% efficient engine and burns fuel having an energy content of 40 MJ/L. If the air resistance and overall frictional forces on this car traveling at highway speeds is 1000 N, what is the overall limit in distance per liter driven on the highway?

A boxer punches a sheet of paper in midair from rest to a speed of 40 m/s in 0.05 s. If the mass of the paper is 0.01 kg, the force of the punch on the paper is

You're driving down the highway and a lovebug spatters onto your windshield. Which undergoes the greater impulse?

A 2-kg mass that weighs 20 N has 40 J of potential energy relative to the ground. What is its height?

A shopping cart moves with a kinetic energy of 40 J. If it moves at twice the speed, its kinetic energy is

In raising a 5000-N piano with a pulley system, for every 1 m of rope pulled down, the piano rises 0.1 m. Ideally, this means the force needed to lift the piano is

A car moves 4 times as fast as another identical car. Compared with the slower car, the faster car has

The ultimate source of energy from fossil fuels is the

An object may have potential energy because of its

A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is

A simple machine CANNOT multiply

A car that travels twice as fast as another car when braking to a stop will skid

Strictly speaking, if any electrical device in an automobile is turned on (such as an air conditioner, headlights, or radio) , more fuel is consumed by the engine. This statement is

If a power plant is 30% efficient, and the transmission system that delivers power to consumers is 60% efficient, then the overall efficiency is

When bullets are fired from an airplane in the forward direction of motion, the momentum of the airplane

A piece of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest. After the putty sticks to the ball, both move with a combined momentum of

Two identical freight cars roll without friction towards each other on a level track. One car rolls at 2 m/s and the other car rolls at 1 m/s. After the cars collide, they couple and roll together with a speed of

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