Chapter 6: Momentum and Collisions

1
Chapter 6 Momentum and Collisions

• Section 1 Momentum and Impulse

2
Objectives

• Compare the momentum of different moving objects.
• Compare the momentum of the same object moving
  with different velocities.
• Identify examples of change in the momentum of an
  object.
• Describe changes in momentum in terms of force
  and time.

3
Linear Momentum

• A bowling ball (and its ability to knock over
• pins) depends on the balls mass as well as its
• speed.
• Are the pins more likely to move rapidly when the
  ball travels at a high speed or at a low speed?

• The pins are more likely to move rapidly when the
  ball travels at a high speed and thus have
  greater momentum.

4
Linear Momentum

• A bowling ball (and its ability to knock over
• pins) depends on the balls mass as well as its
• speed.
• If two bowling balls of different masses move at
  the same speed, which is more likely to move the
  pins?

• The ball with greater mass is more likely to move
  the pins significantly because it has greater
  momentum.

5
Linear Momentum

• Momentum describes an objects motion.
• Momentum is a vector quantity defined as the
  product of an objects mass and velocity.
• It is represented by the symbol p.
• Momentums units are
• It is represented by the following equation.

6
Linear Momentum

• Sample Problem 6A, P. 209
• Classroom Practice 1-3

7
Linear Momentum

• A change in momentum takes force and time. This
  is called impulse.
• The impulse-momentum theorem states that an
  external force applied to an object for a certain
  time interval will cause a change in the objects
  momentum equal to the product of the force and
  the time interval.

8
Linear Momentum

• Sample Problem 6B, P. 211
• Classroom Practice 1-4
• Section Review, P. 214 1-2, 4-5

9
Assignment

• In Class
• Problem 6A 1, 3, 5
• Problem 6B 1, 4, 7
• Homework
• Problem 6A 2, 4, 6
• Problem 6B 2-3, 5-6, 8-9

10
Linear Momentum

• Stopping times and distances depends on the
  impulse-momentum theorem.
• Why is the loaded trucks stopping time twice as
  much as the empty trucks when acted on by the
  same force?

• The loaded trucks momentum is twice as great, so
  its change in momentum is alos twice as great.
  The applied forces are the same, so the time
  period much be twice as great because
  .

11
Linear Momentum

• How do the stopping distances of the trucks
  compare?

• The loaded trucks time period is twice as great
  while its acceleration is half as much
  . Because
• , the loaded trucks
  stopping distance is two times as great as the
  empty trucks.

12
Linear Momentum

• Sample Problem 6C, P. 212
• Classroom Practice 1-3
• Section Review, P. 214 3

13
Assignment

• Homework
• Problem 6C 1-7