Physics Momentum and Collisions Section Review Sheet
Problems
3) A 1.5 kg ball moving at 5.6 m/s directly collides with a wall. The ball rebounds with the same
speed in the same plane.
a) What is the impulse delivered to the ball by the wall?
b) If collision happened in .4 seconds, what was the force applied to the ball by the wall?
4) A 1750 kg car traveling directly South at 25 m/s collides with a 2100 kg car traveling directly East
at 32 m/s. The two cars entangle with each other and move as one object.
Find the final speed and direction of the wreckage.
5) If the ground applies an impulse of 55 N*s to a ball, and the 2 are in contact with each other for
.22 seconds,
a) What is the change in momentum of the ball?
b) What is the impulse delivered to the ball?
c) What is the average force delivered to the ball?
6) A 1800 kg car is driving at a constant 26.5 m/s and runs into a motionless 200 kg Sasquatch. The
Sasquatch interprets this as an act of aggression and hangs onto the car in an attempt to strangle the
driver. Assuming that there is no friction and that the brakes were never applied……
a) what will be the change in momentum of the car/Sasquatch system after the collision?
b) What will be the final velocity of the car/Sasquatch system after the collision?
c) How much kinetic energy was lost in this collision?
7) A 250 kg car travelling at 19 m/s due West collides with a 300 kg car travelling at 22 m/s due East.
The two cars bounce off of each other after the collision. If the 250 kg car is moving at 6 m/s due East
after the collision, what is the velocity of the 300 kg car?
8) As shown in the picture below, a 1.4 kg block and a 1.8 kg block are initially at rest on a frictionless, horizontal
surface. When a compressed spring between the blocks is released, the 1.8 kg block moves to the right at 2.0 m/s, as
shown.
What is the speed of the 1.4-kilogram block after the spring is released?
1.4 Kg
Concepts
1)
Bug hits the windshield of a moving car, which (car or bug) encounters the greatest Impulse? Change
in momentum? Force? Change in velocity?
2) Mass is dumped onto a moving cart (without applying an outside force), what happens to the cart?
3) Why does an egg dropped onto a tile floor break, but when dropped onto a pillow it remains intact?
4) A ball of clay is thrown at a wall, it sticks to the wall and stops…. Explain how momentum is still
conserved here?
5) How is the explosion of a firework and the resulting shape of the explosion a demonstration of
conservation of momentum?
6) Two blocks are squeezed together with a spring between them, the blocks, initially at rest, are then
released. What is the total initial momentum of the system? The final total momentum?
7) Which imparts a greater impulse to an open door…. A tennis ball that bounces or a clay ball of the
same mass that sticks? Which imparts a greater force? Which imparts a greater Δp?
8) Which collision would be the most elastic…. Between two tennis balls…. Or two billiard balls?
9) What is the only type of collision in which kinetic energy is conserved?
10) When a boxer moves his head backwards while receiving a punch…. This technique will effectively do
which of this…. Reduce impulse? Reduce change in momentum? Reduce force? (select all correct
answers)
11) What TWO things is Impulse equal to?
12) A rifle fires a bullet…. Prior to being fired, both objects (the bullet and the gun) were at rest….. which
receives a greater change in velocity? A greater change in momentum? A greater impulse? A
greater force? What was the total initial momentum of the system
13) A 1 kg object is dropped from rest from a height of 8 m, and strikes the ground. Then bounces
upward with a speed of 4 m/s.
a. What speed does it hit the ground with?
b. What impulse is imparted to the ground from the collision?
c. If the ground applied a force of 100 N, how long was the object in contact with the ground?
d. Considering the momentum must be conserved, what must have been the change in
momentum of the Earth during this collision?
14) When a ball is dropped it picks up speed and falls to the ground, because the ball’s speed is
increasing, its momentum is obviously not conserved. Why? In what “system” would the ball’s
momentum be conserved?
15) A 1000 kg truck moving East at 22 m/s is moving toward a 780 kg car moving West at 17 m/s. The two
will collide in a head-on collision in a perfectly inelastic fashion. Will the wreckage come to a
complete stop after the collision? If not, in which direction will the wreckage be moving after the
collision?
16) Often times in an action movie a character will get shot then launch backwards at a high rate of
speed… perhaps through a window pane. Explain using ideas from this chapter why this is unrealistic.
You may use realistic values for items in order to explain. (mass of bullet= .01 kg, speed of bullet =
700 m/s, mass of person =75 kg)