Question 1

A 4-kg ball moving at $$3\ \mathrm{m/s}$$ collides with a stationary 2-kg ball. After the collision, the 4-kg ball moves at $$1\ \mathrm{m/s} in $$the same direction. What is the velocity of the 2-kg ball after the collision, assuming momentum is conserved and the collision is perfectly elastic?

Accepted Answer

$$2\ \mathrm{m/s}$$

Question 2

A bullet of mass $$0.01\ \mathrm{kg} is $$fired at $$400\ \mathrm{m/s}$$ into a stationary block of mass $$2\ \mathrm{kg}$$ resting on a frictionless surface. What is the velocity of the block and bullet together after the collision?

Accepted Answer

$$2\ \mathrm{m/s}$$

Question 3

A $$5\ \mathrm{kg}$$ fish swimming at $$1\ \mathrm{m/s}$$ swallows a $$1\ \mathrm{kg}$$ fish at rest. What is the speed of the larger fish after lunch?

Accepted Answer

$$0.83\ \mathrm{m/s}$$

Question 4

A $$2\ \mathrm{kg}$$ ball is held $$4\ \mathrm{m}$$ above the ground. What is its gravitational potential energy relative to the ground? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$32\ \mathrm{J}$$

Question 5

Two identical carts move at different speeds. The faster cart has twice the speed of the slower cart. How much more kinetic energy does the faster cart have compared to the slower cart?

Accepted Answer

Four times the kinetic energy

Question 6

A $$1.0\ \mathrm{kg}$$ ball traveling at $$4.0\ \mathrm{m/s}$$ strikes a wall and bounces back at $$2.0\ \mathrm{m/s}. $$What is the change in momentum of the ball?

Accepted Answer

$$6\ \mathrm{kg\cdot m/s}$$

Question 7

When Joshua brakes his speeding bicycle to a stop, the kinetic energy is transformed to:

Accepted Answer

Heat

Question 8

If you do work on a skateboard loaded with friends in one-third the usual time, you expend:

Accepted Answer

Three times the usual power

Question 9

A $$500\ \mathrm{N}$$ diver steps off a diving board $$10\ \mathrm{m}$$ above the water. What is the diver's kinetic energy just before hitting the water?

Accepted Answer

$$5000\ \mathrm{J}$$

Question 10

A $$4\ \mathrm{kg}$$ ball with a momentum of $$12\ \mathrm{kg\cdot m/s} is $$moving. What is its speed?

Accepted Answer

$$3\ \mathrm{m/s}$$

Question 11

Which of the following statements about impulse is correct?

Accepted Answer

Impulse is equal to force multiplied by the time it acts.

Question 12

Padded dashboards in cars are safer in an accident than non-padded ones because passengers hitting the dashboard experience:

Accepted Answer

Lengthened time of contact

Question 13

An object has gravitational potential energy due to its:

Accepted Answer

Location

Question 14

Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet?

Accepted Answer

Zero

Question 15

A $$1.5\ \mathrm{kg}$$ cart moving at $$2\ \mathrm{m/s}$$ collides with a $$0.5\ \mathrm{kg}$$ cart at rest. After the collision, the $$1.5\ \mathrm{kg}$$ cart moves at $$1\ \mathrm{m/s} in $$the same direction. What is the velocity of the $$0.5\ \mathrm{kg}$$ cart after the collision?

Accepted Answer

$$3\ \mathrm{m/s}$$

Question 16

When Freddy Frog drops vertically from a tree onto a horizontally-moving skateboard, the speed of the skateboard:

Accepted Answer

Increases

Question 17

If you push a shopping cart twice as far while applying twice the force, the work you do is:

Accepted Answer

Four times as much

Question 18

An object that has kinetic energy must be:

Accepted Answer

Moving

Question 19

Impulse involves the time that a force acts, whereas work involves the:

Accepted Answer

Distance that a force acts

Momentum and Energy: Key Concepts and Applications

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