Physics 432
Impulse & Momentum
1. In a typical collision between a baseball
and bat, the ball (mass = 0.15 kg) has an
initial velocity of 40 m/s in the +x direction
and a final velocity of 45 m/s in the –x
a) Calculate the impulse that the bat exerts
on the ball during the collision.
b) Suppose that the total time of the
collision is 0.6 s. Calculate the average
force exerted on the ball by the bat during
that time.
c) Suppose that the velocity of the bat (mass
= 0.90 kg) just before the ball hits the bat is
30 m/s in the opposite direction to the ball.
Calculate the magnitude and direction of the
velocity of the bat just after the ball
rebounds off the bat.
2. Block 1 of mass of 10 kg initially has a
speed of 15 m/s. It collides with block 2 of
mass 15 kg, which is initially stationary.
After the blocks collide, they stick and move
together along a frictionless surface.
a) What is the momentum of Block 1 before
the collision?
b) What is the momentum of Block 2 before
the collision?
c) What is the momentum of the blocks
combined after the collision?
d) What is the velocity of the blocks after
the collision?
3. Boxcar 1 of mass 5000 kg is moving
down the railroad track with a speed of 8
m/s. It collides and couples to boxcar 2,
which is initially at rest. Together, they
move down the track with a velocity of 4.8
a) What is the momentum of boxcar 1
before the collision?
b) What is the mass of box car 2?
4. A Purdue football player of mass 74 kg
runs at a speed of 13 m/s toward our Illini
defensive line. They collide head on and the
running player is totally stopped.
a) With their helmets on, the players collide
with each other for 0.39 s. Find the average
force exerted on the player’s head.
b) Suppose they were playing 100 years ago
without helmets. Their heads would have
collided for 0.019 s. Find the average force
for this time.
5. A boxcar of mass 1000 kg traveling at 5
m/s strikes another car initially at rest and
then they stick together. After the collision,
the two cars move at a speed of 2 m/s. What
was the mass of the second car?
6. A rifle of mass 2.5 kg fires a bullet with a
mass of 50 g at a velocity of 200 m/s. What
is the recoil velocity of the rifle?
7. Two men push a stalled 800 kg car with a
combined force of 630 N and achieve a final
speed of 3 m/s. How long did the men push
the car?