Momentum and Impulse

Momentum

____ - is the tendency of a moving object to continue moving and the difficulty encountered in reducing that motion

Angular Momentum (𝐿)

_____-is given by where 𝐼 is the moment of Inertia (product of mass and square of the distance from the center of rotation) and 𝜔 is angular velocity.

Impulse

_____- is a force on an object for a time

Impulse

______- is also give by the change in momentum

change in momentum

The sum of the impulses of all forces acting on an object for a certain time is equal to the _____ of the object during that time

• time of collision

• forces of collision
  

Riding the punch increases the ___ of collision and reduces the ____ of collision

Momentum of the body will not change

Conservation of Momentum

• If no external force (like friction) acts on a body, the momentum of the body _____ [will change/will not change]

total momentum is always conserved

In any type of collision (elastic or inelastic), the total momentum is ____[always/not always] conserved.

Elastic Collision

[Elastic Collision/Inelastic Collision] ____ - Kinetic energy is conserved (total KE before = total KE after).

Elastic Collision

[Elastic Collision/Inelastic Collision] ____ - Objects bounce off each other (e.g., billiard balls colliding).

Elastic Collision

[Elastic Collision/Inelastic Collision] ____ - Momentum is conserved

Inelastic Collision

[Elastic Collision/Inelastic Collision] ____ - Kinetic energy is NOT conserved (some energy is lost as heat, sound, or deformation).

Inelastic Collision

[Elastic Collision/Inelastic Collision] ____ - Objects may stick together (e.g., a car crash where vehicles crumple).

Inelastic Collision

[Elastic Collision/Inelastic Collision] ____ - Momentum is still conserved.

1. Once again you are at rest with a grocery cart at the supermarket when you apply a certain force to the cart

for a short time and acquire a certain speed. Suppose you had bought more groceries, enough to double the

mass of the groceries and cart. Neglecting friction, doubling the mass would have what effect on the resulting

final speed if you used the same force for the same length of time? The new final speed would be

a. one-fourth

b. one-half

c. doubled

d. quadrupled

2. In an isolated system, the moment of inertia of a rotating object was doubled. What happens to the angular

velocity of the object?

a. It is quartered.

b. It is halved.

c. It is quadrupled.

d. It is doubled.

3. For how long should a force of 50N be applied to change the momentum of an object by 12kg⋅m/s?

a. 0.24s

b. 62s

c. 4.15s

d. 600s

a. 4.2 𝑚 /𝑠

4. An inelastic collision occurs in one dimension, in which a 15kg block travelling at 5 𝑚 /𝑠 collides with a 10kg block travelling at 3 𝑚/ 𝑠 in the same direction, and they stick together. What are the velocities of the blocks immediately after the collision?

a. 4.2 𝑚 /𝑠

c. 5 𝑚 𝑠

b. 3 𝑚/ 𝑠

d. 3.55 𝑚 /s

a. 2.0 𝑚/𝑠

5. A 2.0-kg meatball is moving with a speed of 6.0 𝑚/ 𝑠 directly toward a 4.0 kg meatball which is at rest. The two meatballs collide and stick together. What is their velocity immediately after the (inelastic) collision?

a. 2.0 𝑚/𝑠

c. 4.0 𝑚/𝑠

b. 3.0 𝑚/𝑠

d. 5.0 𝑚/𝑠