Q: A puck slows to a halt on ice. Is the system interacting with the environment, and does $$\Delta \vec{p} = 0$$ for the puck?

Yes, the system is interacting; $$\Delta \vec{p} \neq 0$$

Question 1

A block slides across three different surfaces: ice, polished wood, and concrete. Which surface will cause the block to stop in the shortest amount of time, and why?

Accepted Answer

Concrete, because it has the highest friction.

Question 2

Which of the following best describes inertia?

Accepted Answer

The tendency of an object to resist any change in its velocity.

Question 3

Two identical carts collide on a frictionless track. Cart 1 is initially at rest, and Cart 2 moves toward it. After the collision, Cart 1 moves with the initial velocity of Cart 2, and Cart 2 is at rest. What does this demonstrate?

Accepted Answer

The velocities of the carts are exchanged during the collision.

Question 4

If a cart with twice the mass of a standard cart collides with a standard cart, how does the change in velocity of the double-mass cart compare to the standard cart?

Accepted Answer

It is half as large and in the opposite direction.

Question 5

Which of the following statements about inertia is correct?

Accepted Answer

Inertia depends on both the type and amount of material in an object.

Question 6

Which of the following is an extensive property?

Accepted Answer

Inertia

Question 7

A system is defined as:

Accepted Answer

Any object or group of objects separated from their environment for analysis.

Question 8

Which equation correctly expresses the conservation of momentum for two colliding objects in an isolated system?

Accepted Answer

$$\Delta \vec{p}_1 + \Delta \vec{p}_2 = 0$$

Question 9

A 0.20 kg rubber ball is dropped from a height and bounces straight up with the same speed it had before hitting the floor. What is the impulse delivered by the floor to the ball if the speed just before and after is $$4.4\ \mathrm{m/s}$$?

Accepted Answer

$$1.8\ \mathrm{kg \cdot m/s}$$

Question 10

Which of the following best describes the relationship between symmetry and conservation laws in physics?

Accepted Answer

Every symmetry in the laws of physics corresponds to a conserved quantity (Noether's Theorem).

Question 11

A rocket is propelled forward by ejecting gas at high speed. This forward motion is a consequence of:

Accepted Answer

Conservation of momentum.

Question 12

Suppose you are on a cart at rest on a frictionless track. You throw balls at a partition rigidly mounted on the cart, and the balls bounce straight back. What happens to the cart?

Accepted Answer

It moves to the left.

Question 13

Which of the following is NOT a way that an extensive property of a system can change?

Accepted Answer

Multiplication

Question 14

A ball moving at speed $$v is $$brought to rest, then projected backward to its original speed. In which case(s) does the ball undergo the largest change in momentum?

Accepted Answer

(c) Only

Question 15

Which of the following is the correct formula for the momentum $$\vec{p} of an $$object?

Accepted Answer

$$\vec{p} = m \vec{v}$$

Question 16

If a system is isolated, what can be said about the total momentum of the system?

Accepted Answer

It remains constant.

Question 17

Which of the following is an example of an intensive property?

Accepted Answer

Temperature

Question 18

A puck slows to a halt on ice. Is the system interacting with the environment, and does $$\Delta \vec{p} = 0$$ for the puck?

Accepted Answer

Yes, the system is interacting; $$\Delta \vec{p} 
eq 0$$

Question 19

Which of the following best describes the impulse delivered to an object?

Accepted Answer

The change in momentum of the object.

Chapter 4: Momentum – Friction, Inertia, Systems, and Conservation

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