Question 1

A bullet strikes and passes through a carrot, as shown in the image. Which principle allows us to analyze the motion of the bullet and carrot after the collision, even if the forces involved are unknown?

Accepted Answer

Conservation of momentum

Question 2

Which equation expresses Newton’s second law in terms of momentum?

Accepted Answer

$$\sum \vec{F} = \frac{d\vec{p}}{dt}$$

Question 3

A baseball pitcher throws a ball. The kinetic energy gained by the ball is equal to:

Accepted Answer

$$\sum \vec{F} \cdot \vec{s}$$

Question 4

The impulse delivered by a constant net force $$\vec{F}$$ acting over a time interval $$\Delta t is$$:

Accepted Answer

$$\vec{J} = \sum \vec{F} \Delta t$$

Question 5

If two forces act for different durations but the area under their force vs. time curves is the same, what can be said about the impulses delivered?

Accepted Answer

Both forces deliver the same impulse

Question 6

According to the impulse-momentum theorem, the impulse $$\vec{J}$$ delivered to a particle equals:

Accepted Answer

$$\vec{J} = \vec{p}_f - \vec{p}_i$$

Question 7

Why is it safer to land with knees bent after jumping, rather than with legs extended?

Accepted Answer

Bending knees increases the time to stop, reducing the force on the legs

Question 8

In an isolated system, such as two astronauts pushing off each other in space, what happens to the total momentum?

Accepted Answer

It remains constant

Question 9

When analyzing the momentum of a system of particles, why must vector addition be used?

Accepted Answer

Because the direction of each particle's momentum matters

Question 10

In a one-dimensional elastic collision between two bodies A and B, where B is initially at rest, what is the final velocity of B?

Accepted Answer

$$v_{B2x} = \frac{2m_A}{m_A + m_B} v_{A1x}$$

Question 11

What distinguishes a completely inelastic collision from an elastic collision?

Accepted Answer

Objects stick together after collision in a completely inelastic collision

Question 12

A car crash is designed to be inelastic. What happens to the kinetic energy during the collision?

Accepted Answer

It is absorbed by the car structure and lost to deformation

Question 13

In a 1-D elastic collision between two equal-mass objects, where one is initially at rest, what happens after the collision?

Accepted Answer

The moving object stops and the stationary object moves with the original speed

Question 14

The center of mass of a system of particles is given by:

Accepted Answer

$$\vec{r}_{cm} = \frac{\sum m_i \vec{r}_i}{\sum m_i}$$

Question 15

If a shell explodes in mid-air, what happens to the center of mass of the fragments?

Accepted Answer

It follows the original trajectory of the shell

Question 16

A rocket ejects burned fuel at high speed. How does this affect the rocket’s momentum?

Accepted Answer

The rocket’s momentum increases due to the momentum of the ejected fuel

Question 17

The total momentum of a system is related to the velocity of the center of mass by:

Accepted Answer

$$M \vec{v}_{cm} = \vec{P}$$

Question 18

In a collision where external forces can be neglected, what is always conserved?

Accepted Answer

Total momentum

Question 19

Which scenario best illustrates an elastic collision?

Accepted Answer

Billiard balls collide and bounce apart

Question 20

A disk and a donut both have an axis of symmetry. Where is their center of mass located?

Accepted Answer

Along the axis of symmetry

Momentum, Impulse, and Collisions – Study Notes

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