Honors Physics: Chapter 8 Linear Momentum Test Review

Key Points in this chapter:

Momentum

Impulse

Conservation of Momentum

Inelastic Collisions

Elastic Collisions

Momentum In 2 Dimensions

What is momentum?

Quality of motion an object has

Momentum is the product of:

Mass and velocity

The equation for momentum is:

p=mv=\left(\operatorname{kg}\cdot\frac{m}{s}\right)

Is momentum a vector or scaler quantity?

Vector quantity

What is impulse?

Change in momentum

To change momentum….

Apply a force for a period of time

Apply force for a larger period of time=

Larger momentum change

Equation for impulse:

J=\Delta p=mv2-mv1=m\Delta v=F\cdot t=\left(N\cdot s\right),F=ma=m\frac{\Delta v}{t}^{}-->m\Delta v=F\cdot t

Impulse equation to reduce force:

F\cdot t=m\Delta v=F\cdot t

What is conservation of momentum?

Total momentum of a closed system remains constant

What does closed system mean?

No net external forces

What is the equation for conservation of momentum?

\Sigma p1=\Sigma p2\rightarrow mv1+mv2=mv1^{\prime}+mv2^{\prime}

Perfectly inelastic collision when momentum is conserved is:

Objects stick together and travel at same velocity after collision

During perfectly inelastic collision momentum is:

Conserved

During perfectly inelastic collision kinetic energy is:

LOST

During elastic collision kinetic energy is:

Conserved

Equation for perfectly inelastic collision:

m1v1+m2v2=(m1+m2)v2’

During perfectly elastic collision momentum is:

Conserved

During perfectly elastic collision the relative velocity is the _____ before and after collision, but in the ________ direction.

Same ; Opposite

What is relative velocity?

The difference in velocity between two objects

Equations used for perfectly elastic collision:

m1​v1​+m2​v2​=m1​v1′​+m2​v2′​​ AND v2-v1=v1’-v2’

What is the product of an object's mass and its velocity?

Momentum

Which of the following has the greatest momentum?

a 1.6 x 103 kg car moving at 0.5 m/s

How does the momentum of an object change if the object's velocity doubles?

The momentum doubles

What are the units of momentum?

kg•m/s

Which of the following can determine the magnitude of the change in an object's momentum?

Force and time interval

Which of the following is true of changes in momentum?

A large force may produce a small change in momentum by acting over a short time interval.

If a net force acts on an object, then the object's momentum

will either increase or decrease.

Which of the following involves a change in momentum?

A spacecraft travels at constant speed while slowly losing mass.

A batter hits a baseball back to the pitcher at the same speed as the pitch. Which of the following is true?

The magnitude of the ball's momentum is the same before and after the batter hits the ball.

A small marble collides with a billiard ball that is initially at rest.

Which of the following is true?

The momentum of the billiard ball increases, and the momentum of the marble decreases.

When two ice skaters initially at rest push off one another, their final momenta are

equal in magnitude and opposite in direction.

When two objects interact in an isolated system,

the total momentum is always conserved

Which of the following expresses the law of conservation of momentum?

The total momentum of an isolated system remains constant regardless of the forces between the objects in the system.

Conservation of momentum follows from

Newton's third law.

A billiard ball hits the edge of another billiard ball that is initially at rest. The second ball moves off at an angle. Which of the following is true?

The momentum lost by the first ball is gained by the second ball.

A croquet ball moving at 2.0m/s strikes another ball of equal mass.

The first ball stops moving after the collision. What is the velocity of the second ball after the collision?

2 m/s

Describe the changes in momentum that take place when two billiard balls of equal mass but moving at different speeds collide head-on.

Momentum is conserved and the faster ball loses momentum and the slower ball gains momentum by the same amount

Collisions in 2D:

Vector Sum of momentum before collision is equal to vector sum after collision.

Equation for Impulse in 2D:

∆𝑝 = 𝑝2 − 𝑝1 = 𝑝2 + (−𝑝1)