Transcript Momentum & Impulse

Newton’s 3rd Law,
Momentum
&
Impulse
Newton’s 3rd Law of Motion
For every action there is an equal
and opposite reaction. (All forces
come in pairs)
Action and Reaction pairs
Effect of different masses
Forces the same, accelerations are different!!!!
What does it mean to say “roll with the
punches?”
Why is it important to wear a helmet?
Is it a good thing that cars basically crumble in
an accident?
Momentum
What is momentum?
Momentum is:
Inertia in motion… or mass in motion
Momentum (p) is the mass of an object
multiplied by its velocity:
p = mv
Units:
Momentum is measured in kgm/s
Can these two
things have
the same
momentum?
Which of these will
have the greater
inertia? How do
you know?
How can
have the same momentum as
?
The little girl can have the same
momentum as the elephant if, when
they are moving, her velocity is much
greater than that of the elephant.
Impulse
What is impulse?
The Egg Test!
Impulse
Forces change motion, so velocity
changes
If velocity changes, momentum
changes
Amount of momentum change depends
on how long we apply the force
Impulse:
Impulse is the Force exerted on an object
in a certain amount of time:
Impulse (J) = force times time
J=Fxt
Impulse results in a change in momentum.
Therefore:
Ft = ∆mv
Can we prove it:
Conservation of Momentum
What does it mean to say the word:
CONSERVE
Conservation of Momentum
All momentum is conserved before an
event and after an event.
In other words. No momentum is ever
lost. What we start with is what we end
with. The TOTAL momentum never
changes.
The rubber ball paradox
Elastic and Inelastic
What does it mean to be Elastic?
What does it mean to be Inelastic
Elastic vs Inelastic Collisions
Elastic Collision: a collision when a
object bounces off another object
(they don’t stick together)
Inelastic Collision: when two
objects stick together (don’t bounce
off each other)