Lesson 7: Momentum

Question 1

What is momentum?

Answer 1

Momentum is defined as an object’s mass x velocity

Question 2

What are the units for momentum?

Answer 2

kg * m/s

Question 3

What is Impulse?

Answer 3

Impulse is the force applied to an object multiplied by the time over which that force is applied.

Impulse can also be defined as an objects change in momentum (Impulse Momentum Theorem)

Question 4

What are the units for impulse?

Answer 4

kg*m/s

Question 5

When is momentum conserved?

Answer 5

When no external forces are acting on a system

Question 6

Conservation of Momentum Equation

Answer 6

m1v1o + m2v2o = m1v1f + m2v2f

Question 7

What type of collision conserves momentum?

Answer 7

All collisions conserve momentum as long as no external forces are acting on the sytem

Question 8

What type of collision conserves kinetic energy?

Answer 8

kinetic energy is only conserved in perfectly elastic 1D collisions

Question 9

What are the two types of 1D collisions?

Answer 9

Elastic and Inelastic Collisions

Question 10

An object moving to the right collides with another object moving to the left. After the objects collide, they stick together and move to the right. What type of collisions is this and what does the conservation of momentum equation for this collision look like?

Answer 10

Perfectly inelastic collision

m1v1o + m2v2o = vf(m1 +m2)

Question 11

A projectile is fired from a weapon. What type of collision is this an example of and what does the conservation of momentum equation for this collision look like?

Answer 11

Reverse inelastic collision

vo(m1 + m2) = m1v1f + m2v2f

Question 12

What is another equation we can use when we have a perfectly elastic 1D collision?

Answer 12

v1o - v2o = v2f - v1f

equation is derived from conservation of kinetic energy and conservation of momentum. It can only be used in perfectly elastic 1D collisions

Question 13

An object moving to the north collides with an object moving to the west. The objects stick together after the collision. Can we use conservation of momentum to find the final velocity?

Answer 13

Yes, but we need to consider the conservation of momentum in both the x and y direction since the objects are moving in two dimensions

Question 14

An object collides with an object at rest at a glance. After the collision both objects scatter in different directions. What time of collision is this? Can we use the conservation of momentum in this case?

Answer 14

This is a glancing collision and yes but because the objects scatter and move in different directions we need to consider the conservation of momentum in both the x and y directions

Question 15

Conservation of Kinetic Energy Equation

Answer 15

KEo1 + KEo2 = KEf1 + KEf2

Question 16

An object moving to the right collides with another object head on. After the collision, the first object moves to the left and the second object moves to the right. What type of collision is this? What does the conservation of momentum equation look like for this collision?

Answer 16

Perfectly Elastic Collision

m1v1o + m2v2o = m1v1f + m2v2f