Transcript Impulse & Momentum

Impulse & Momentum
Chapter 9
Playing Baseball
Explain what happens to the baseball
when the batter hits the ball
 What happens to the bat?
 Explain what happens when the
outfielder catches the ball

Impulse & Momentum
Graph on page 230 shows how the
force changes with time as the bat and
ball are in contact.
 Check out the time. 3 ms
 Newton’s 2nd law states that a net force
causes an acceleration

 v 
F  m a  m 
 t 
Rearrange
Ft  mv
Impulse
 The
product of the average
force on the object and the time
interval over which the force
acts
 Impulse=FΔt
Momentum
 The
product of mass and
velocity
 r=mv
 r is a Greek letter representing
momentum
 Units kilogram.meter/second
Impulse-Momentum Theorem

The impulse on an object equals the
change in momentum of the object
Ft  p f  pi
Using the Impulse-Momentum
Theorem
Remember that velocity is a vector
quantity so that make momentum a
vector quantity.
 A baseball comes into the bat with a
positive velocity and leaves with a
negative velocity.

Using the Impulse-Momentum
Theorem to Save Lives
 How
do you reduce the sting in
catching a ball?
 How can you catch an egg in a
sheet without the egg breaking?
 Explain with the ImpulseMomentum Theorem why air bags
save lives.
 How
do you reduce the sting
in catching a ball?
 How can you catch an egg in
a sheet without the egg
breaking?
 How could the force of air
bags be reduced?