Transcript Momentum & Impulse - Bedford Public Schools

Momentum
&
Impulse
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?
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.
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
Impulse
What is impulse?
The Egg Test!
Impulse:
Impulse is a change in momentum. It
occurs when a force is exerted on an
object over a certain amount of time:
Impulse (J) = force times time
J=Fxt
Can we prove that:
Ft = ∆mv
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: When an object
collides with another object and
returns back to its original form.
-a collision when a object bounces
off another object (they don’t stick
together)
Inelastic Collision: When an
object collides with another object
and does not return to its original
form.
-when two objects stick together
(don’t bounce off each other)
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.
Conservation of Momentum Problem:
A 7000kg truck moving with a velocity of 8m/s runs into and
sticks to the back of a parked car that has a mass of 2000kg.
What is the velocity of the combined cars after they collide?
#2
An Ice Hockey puck with mass 2kg is moving with a velocity
of 3m/s. It then collides with a stationary rok that has a mass
of .5 kg. If the rok bounces off the puck with a velocity of
4m/s, how fast is the puck moving?