April 3rd, 2014
Homework: Study for test on Tuesday 4/8:
Study Guide is online Force packet page: 9/10 due for check in
tomorrow- Read pg. 60-61

Do Now
 Update T.O.C: pg. 16 Conservation of
Momentum
 Open Notebooks to pg. 15
 Open textbooks to pg. 56
What do you know about Action- Reaction
forces… List examples- pg. 15: in NB
What are some everyday activities that would not be
possible with out action-reaction forceslook at fig. 15 on pg. 56
Example : 2 Skaters pushing against each other
Newton’s Third Law?
Why don’t the action and
reaction forces cancel each
other out?

They do not cancel each other because they
act on different objects
She exerts an upward action
force on the ball
 The ball exerts an equal but
opposite downward force
back on her wrists

Apply Newton’s 3rd Law of motion to a
pogo stickWhat are the action-reaction
forces in a pogo stick jump?

Action Forces-

Reaction Forces-
Momentum- How much it is moving
Momentum
•An objects momentum depends on
velocity and mass
Momentum…

If these two objects are moving at the
same velocity… which has a greater
momentum?
Momentum = Mass x Velocity

What is the momentum of a 5kg object
moving at a velocity of 6 m/s
Conservation of Momentum
The Law of conservation
of momentum states:
*When two objects
collide momentum is not
lost, it is transferred
from one object to
another object -- if there
is no unbalanced forces
acting– like friction.

http://www.youtube.com/watch?v=W9Eq
U1_DXUw
http://www.youtube.com/watch?v=qNou0xg3_cY
Figure 18- pg. 60

In part A, why does the blue car move more
slowly after the collision?
◦ Some of its momentum is transferred to the
green car
Using fig. 16 Answer the following
questions in your notebook on pg 16:
 What happens to an objects
momentum if they collide when:

◦ Both objects are moving
◦ One object is moving and the other is not