Question 1

A 2 kg ball is moving at 3 m/s. What is its momentum?

Accepted Answer

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

Question 2

If the velocity of an object is doubled while its mass remains constant, what happens to its momentum?

Accepted Answer

It doubles.

Question 3

A 0.5 kg baseball is hit with a force of $$100\ \mathrm{N}$$ for $$0.02\ \mathrm{s}. $$What is the impulse delivered to the ball?

Accepted Answer

$$2\ \mathrm{N \cdot s}$$

Question 4

A car crashes into a haystack and comes to rest in $$0.5\ \mathrm{s}. If $$the same car crashes into a brick wall and comes to rest in $$0.05\ \mathrm{s}$$, which scenario results in a greater force on the car?

Accepted Answer

The brick wall, because the time is shorter.

Question 5

Which of the following best describes the law of conservation of momentum?

Accepted Answer

The total momentum of a system remains constant if no external force acts on it.

Question 6

A 1000 kg car moving at $$10\ \mathrm{m/s}$$ collides and couples with a stationary 1000 kg car. What is their speed after the collision?

Accepted Answer

$$5\ \mathrm{m/s}$$

Question 7

A karate expert breaks a stack of bricks with a swift blow. Why is the force on the bricks so large?

Accepted Answer

Because the time of contact is very short.

Question 8

A ball bounces off a wall with the same speed it had before impact. Compared to stopping the ball, the impulse needed to bounce it is:

Accepted Answer

Twice as large.

Question 9

Which of the following is true for an elastic collision?

Accepted Answer

Kinetic energy and momentum are both conserved.

Question 10

A firecracker explodes at rest into three pieces. What is the vector sum of the momenta of the pieces after the explosion?

Accepted Answer

Zero.

Question 11

A golfer follows through with a swing to hit a golf ball. Why does this increase the ball's momentum?

Accepted Answer

It increases the time the force acts on the ball.

Question 12

A moving object has which of the following properties?

Accepted Answer

All of the above.

Question 13

A 0.2 kg ball moving at $$5\ \mathrm{m/s}$$ bounces off a wall and returns with $$-5\ \mathrm{m/s}. $$What is the magnitude of the change in momentum?

Accepted Answer

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

Question 14

Two cars collide at a right angle at an intersection. How do you find the total momentum after the collision?

Accepted Answer

Use vector addition to find the resultant momentum.

Question 15

A dish falls and lands on a carpet or a hard floor. Which of the following is true about the change in momentum?

Accepted Answer

It is the same in both cases.

Question 16

A cannon fires a cannonball. What happens to the momentum of the cannon and the cannonball?

Accepted Answer

Both gain equal and opposite momentum.

Question 17

Which of the following best explains why airbags in cars reduce injuries during collisions?

Accepted Answer

They increase the time over which the passenger's momentum is brought to zero.

Question 18

A 3 kg object moving at $$4\ \mathrm{m/s}$$ comes to rest in $$2\ \mathrm{s}$$ due to a constant force. What is the magnitude of the force?

Accepted Answer

$$12\ \mathrm{N}$$

Momentum and Its Conservation: Physics with Calculus Study Notes

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