Transcript Momentum and impulse

MOMENTUM AND IMPULSE
Let’s start with everyday
language

What do you say when a sports
team is on a roll?

They may not have the lead but
they may have ___________
MOMENTUM

A team that has momentum is
hard to stop.
What is momentum?
 Momentum:
p=mass x velocity
 What does this mean in the physical world?
 Which is harder to stop a soccer ball or a
bowling ball moving at the same speed?
Explain why?
 What about a bullet?
Explain why?
Momentum
 Momentum is a vector quantity.
What is Conservation?
 Conserved describes a quantity that may
change during some process, but does NOT
appear from nowhere or disappear without a
trace.
 In an isolated system, certain physical
quantities are conserved, such as mass and
energy.
 Let’s see how it works!
How can we represent
conservation?
Is Momentum Conserved?
 When there is a collision between two objects,
Newton's Third Law states that the force on one
of the bodies is equal and opposite to the force
on the other body.
 Therefore, if no other forces act on the bodies (in
the direction of collision), then the total
momentum of the two bodies will be unchanged.
 Hence the total momentum before collision in a
particular direction = total momentum after in a
particular direction.
What happens during a
collision?
Types of Collisions
10
To change the momentum of a body, a
force must be applied to the mass. The
longer this force is applied to the mass, the
greater effect it will have on changing the
momentum.
IMPULSE – A force applied for a period of time
which results in a change of momentum
Why does an egg break or not
break?
 An egg dropped on a tile floor breaks, but an egg
dropped on a pillow does not. Why?
FΔt= mΔv
In both cases, m and Δv are the same.
If Δt goes up, what happens to F, the force?
Right! Force goes down.
When dropped on a pillow, the egg starts to slow
down as soon as it touches it. A pillow increases
the time the egg takes to stops.
Car Crash
Would you rather be in a
head on collision with an
identical car, traveling at
the same speed as you, or
a brick wall?
Assume in both situations you
come to a complete stop.
Take a guess!
http://techdigestuk.typepad.com/photos/uncategorized/car_crash.JPG
Car
The Crash
answer is…(cont.)
It Does Not Matter!
Look at FΔt= mΔv
In both situations, Δt, m, and Δv
are the same!
The time it takes you to stop
depends on your car, m is the
mass of your car, and Δv
depends on how fast you
were initially traveling.