April 3rd, 2014

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
 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
•An objects momentum depends on
velocity and mass
If these two objects are moving at the
same velocity… which has a greater
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.
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

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