This document provides an overview of the key concepts in the chapter on linear momentum including: - Defining linear momentum as the product of an object's mass and velocity. - Explaining how momentum is related to force through Newton's second law. - Describing how the total momentum of an isolated system remains constant through the law of conservation of momentum.

1. Linear
Momentum
Chapter 7

2. • How do we define momentum?
• How is momentum related to force?
• How can we apply the conservation of
momentum?
Momentum and its
Relation to Force

3. • http://www.youtube.com/watch?v=0LnbyjOyEQ8&featur
e=related
Momentum

4. • Linear Momentum: the product of an objects mass and
its velocity
• Symbol is p
• Units are kg·m/s
Momentum

5. •
Momentum

6. • A smaller football player can have the same momentum
as a larger one, if…
• Application?
• Direction change?
Momentum

7. •
Relation to Newton’s 2nd

8. • For a top player, a tennis ball may leave the racket on the
serve with a speed of 55 m/s (about 120 mph). If the ball
has a mass of 0.060 kg and is in contact with the racket
for about 4 x 10-3 s, estimate the average force on the ball.
• Would this force be large enough to lift a 60 kg person?
Force of a tennis serve

9. • Water leaves a hose at
a rate of 1.5 kg/s with
a speed of 20 m/s and
is aimed at the side of
a car, which stops it.
What force is exerted
by the water on the
car?
Water

10. • During a collision,
measurements show
that the total
momentum does not
change
Conservation of
Momentum

11. •
Conservation of
Momentum

12. The total momentum of an
isolated system remains
constant

13. • A 10,000 kg railroad car, A, traveling at a speed of 24.0
m/s strikes an identical car, B, at rest. If the cars lock
together as a result of the collision, what is their common
speed just afterward?
Railroad cars

14. • Only applies to an isolated system
• Only forces are between objects in the system
• System of rock falling by itself will not conserve
momentum, because an external force, gravity
• If we expand the system to include the Earth, then we can
conserve momentum
Systems

15. • Momentum
conservation works
for a rocket as long as
we consider the
rocket and its fuel to
be one system, and
account for the mass
loss of the rocket.
Systems

16. • Read Sections 7.1 and 7.2
• Do Problems # 1 – 12, Page 188
Homework