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)

What is the SI unit of momentum?

N • s

When a cannon fires a cannonball, the cannon will recoil backward because the

momentum of the cannonball and cannon is conserved.

A freight car moves along a frictionless level railroad track at constant speed. The car is open on top. A large load of coal is suddenly dumped into the car. What happens to the velocity of the car?

It decreases.

A rubber ball and a lump of putty have equal mass. They are thrown with equal speed against a wall.

The ball bounces back with nearly the same speed with which it hit. The putty sticks to the wall. Which objects experiences the greater momentum change?

the ball

A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the magnitude of the average collision force is correct?

The small car and the truck experience the same average force.

A Ping-Pong ball moving east at a speed of 4 m/s, collides with a stationary bowling ball. The Ping-Pong ball bounces back to the west, and the bowling ball moves very slowly to the east. Which object experiences the greater magnitude impulse during the collision?

Neither; both experienced the same magnitude impulse.

A 100-kg football linebacker moving at 2.0m/s tackles head-on an 80-kg halfback running 3.0 m/s.

Neglecting the effects due to digging in of cleats,

the halfback will drive the linebacker backward.

In an elastic collision, if the momentum is conserved, then which of the following statements is true about kinetic energy?

Kinetic energy is also conserved.

In a game of pool, the white cue ball hits the #5 ball and stops, while the #5 ball roves away with the same velocity as the cue ball had originally. The type of collision is

elastic

A very heavy object moving with speed v collides head-on with a very light object at rest. The collision is elastic, and there is no friction. The heavy object barely slows down. What is the speed of the light object after the collision?

nearly 2v

A red ball with a velocity of +3.0 m/s collides head-on with a yellow ball of equal mass moving with a velocity of -2.0 m/s. What is the velocity of the yellow ball after the collision?

+3.0 m/s

In an inelastic collision, if the momentum is conserved, then which of the following statements is true about kinetic energy?

Kinetic energy is lost.

Two objects collide and stick together. Kinetic energy

is definitely not conserved.

A small object collides with a large object and sticks. Which object experiences the larger magnitude of momentum change?

Both objects experience the same magnitude of momentum change.