Q: Which of the following is the correct mathematical expression for impulse?

$$I = F \times t = \Delta (mv)$$

Question 1

Which of the following best describes the physical quantity carried by a moving car?

Accepted Answer

Momentum

Question 2

A 4 kg ball has a momentum of 12 kg m/s. What is the speed of the ball?

Accepted Answer

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

Question 3

If the speed of an object is doubled, its momentum:

Accepted Answer

Doubles

Question 4

Two billiard balls of equal mass and speed roll toward each other and collide head-on. What is their combined momentum after the collision?

Accepted Answer

$$0$$

Question 5

A single car of mass $$m$$ moving at $$10\ \mathrm{m/s}$$ collides inelastically with another car of the same mass at rest. What is the final velocity $$V of $$the combined system?

Accepted Answer

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

Question 6

Suppose a 10 kg bowling ball is at rest and a 0.01 kg piece of putty is sent toward it at $$100\ \mathrm{m/s}. $$After an inelastic collision, what is the total momentum of the system?

Accepted Answer

$$1\ \mathrm{kg\ m/s}$$

Question 7

Which of the following statements about the law of conservation of momentum is correct?

Accepted Answer

Momentum of a system is conserved in the absence of external forces.

Question 8

Two boxes, one of mass $$2\ \mathrm{kg}$$ and the other $$1\ \mathrm{kg}$$, are at rest on a frictionless surface. An explosion pushes them apart. If the $$1\ \mathrm{kg}$$ box moves at $$6\ \mathrm{m/s}$$, what is the speed of the $$2\ \mathrm{kg}$$ box?

Accepted Answer

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

Question 9

A rocket is initially at rest. After ignition, the exhaust gases are expelled backward. What happens to the rocket's momentum?

Accepted Answer

It remains zero, as the forward momentum of the rocket equals the backward momentum of the exhaust.

Question 10

When a firecracker explodes, the momenta of its fragments:

Accepted Answer

Add up to the original momentum of the firecracker.

Question 11

Two objects of the same size and shape, but different masses, are dropped from a tower (neglecting air resistance). When they reach the ground, the heavier one has:

Accepted Answer

Greater momentum

Question 12

What is impulse?

Accepted Answer

Change in momentum

Question 13

Which of the following is the correct mathematical expression for impulse?

Accepted Answer

$$I = F 	imes t = \Delta (mv)$$

Question 14

Why does a wine glass often not break when it falls onto a carpeted floor compared to a stone floor?

Accepted Answer

The stopping time is longer on the carpet, reducing the force of impact.

Question 15

During a head-on collision between a car and a bug, which of the following quantities is exerted on both with equal magnitudes?

Accepted Answer

All of these

Question 16

A karate expert splits a stack of bricks by bringing her arms down swiftly. Why is the time of contact important for the force exerted?

Accepted Answer

A shorter contact time results in a greater force for the same change in momentum.

Question 17

Which of the following is true about elastic and inelastic collisions?

Accepted Answer

Total momentum is conserved in both types of collisions.

Question 18

A car of mass $$m$$ moving at velocity $$v$$ collides with a stationary car of mass $$2m in a $$perfectly inelastic collision. What is the final velocity $$V of $$the combined mass?

Accepted Answer

$$V = \frac{v}{3}$$

Question 19

Which of the following best explains why airbags are necessary in cars?

Accepted Answer

They increase the time over which momentum is reduced, decreasing the force of impact.

Question 20

A moving boulder and a stone are rolling at the same speed. Which has greater momentum and why?

Accepted Answer

The boulder, because it has greater mass.

module 4 lecture 7: Momentum, Collisions, and Impulse

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