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1. What is the momentum of each of these objects?
a) a ball of mass 0.50 kg moving up at 30 m/s
b) a 200 kg truck moving 10 m/s[S]
c) an electron moving at 1.0 X 107 m/s if its mass is 9.11 X 10-31 kg
d) a planet moving with a velocity of 3.0 X 104 m/s, if its mass is 6.0 X 1024 kg
2. Determine the impulse in each of these cases.
a) A dynamics cart has a force of 25 N[E] acting on it for 3.2 s.
b) A baseball bat exerts a force of 120 N for 0.05 s on the ball.
c) It takes 3.0 s for the Earth to pull a 12 kg crate down an empty elevator shaft.
d) A collision between objects produces the following force time graph.
e) A radio operated toy car runs into the tire of a parked car. The force time graph
for the collision is given below.
3. A 200 g ball moving at 1.0 m/s roles against the foot of a person who is walking. The
rebound speed of the ball is 2.0 m/s.
a) Determine the change in momentum of the ball.
b) Calculate the impulse given to the ball due to the collision.
4. A boy who is playing hockey on a pond hits the puck which travels at 10 m/s. The puck
of mass 0.20 kg slides into some snow and emerges 2.5s later with a speed of 2 m/s.
a) Calculate the puck's change in momentum.
b) Determine the impulse of the snow on the puck.
c) Find the average frictional force exerted on the puck while in the snow.
5. A skateboarder kicks a 2.0 kg skateboard, which causes its speed to increase to 4.5 m/s
in 0.50 s. Assuming that the direction of motion does not change, and that the average
force exerted is 6.0 N, determine the initial speed of the the skateboard.
6. The acceleration of a vehicle is 4.0 m/s2. The vehicle, which has a mass of 1.5 X 103 kg,
accelerates from rest for 6.0 s.
a) After 6.0 s what is the momentum of the vehicle?
b) Determine the impulse on the vehicle.
7. A baseball bat is in contact with a golf ball for 5.0 X 10-4 s. The average force between
the ball and bat is 7.2 X 103 N.
a) What is the impulse on the ball?
b) Determine the velocity of the golf ball, which has a mass of 45 g, when it is no
longer in contact with the bat.
8. A small rocket of mass 5.0 kg has an average accelerating force of 5.0 X 104 N applied
to it during launch. The final velocity of the rocket is 200 m/s.
a) What is the impulse on the rocket?
b) Determine the time it takes for the rocket to reach maximum speed.
9. A ball of mass 0.300 kg moves towards home plate at 50 m/s. After being hit, the ball
has a speed of 100 m/s in the opposite direction. If the impact time is 2.0 X 10-2 s, what
is the average force exerted on the ball?
10. An empty 5.000 X 103 kg boxcar is rolling at 5.2 m/s. It runs into a partly loaded boxcar
of mass 8.000 X 103 kg which is sitting motionless on the track. After collision, they are
hooked together. Determine their speed after colliding.
11. A person of mass 75 kg jumps onto a wagon of mass 10 kg. The person was running at
3.0 m/s, and the wagon was rolling at 2.0 m/s in the same direction. What will the final
velocity of the wagon and person be?
12. A steel sled of mass 25 kg is moving at 3.0 m/s [right] when it collides with a 15 kg steel
sled moving at 6.0 m/s [left]. Assuming there is no friction, what is the velocity of the 25
kg sled after collision, given that
a) the 15 kg sled moves at 0.30 m/s [left] after collision.
b) the 15 kg sled rebounds at 0.45 m/s [right] after collision.
c) The two sleds sticks together.
13. A rocket car trying to beat the record speed for a vehicle moving on land, has a mass of
1.4 X 104 kg. The car moves forward by expelling gases from its engines at a rate of
10 kg/s. The speed of the exhaust is 2.5 X 104 m/s relative to the car. If the car starts
from rest determine the length of the burn in order for the car to reach a speed of 50
m/s. Ignore the fact that the mass of the car decreases because of the gas ejected.
14. A bullet is fired into a wooden block which is secured firmly to the Earth. The mass of
the bullet is 0.50 kg, and it moves at 400 m/s. The penetration distance into the wooden
block is 0.10 m Assuming a constant force between the bullet and the wooden block,
calculate:
a) the bullet's acceleration.
b) the average force exerted on the bullet
c) how long the bullet takes to stop once it contacts the wooden block.
d) the collision's impulse.
e) the momentum of the bullet before striking the block.
15. A stationary car of mass 1.0 X 103 kg is rammed from behind by another car of mass
1.2 X 103 kg and moving at 20 m/s. Determine how fast the cars will be moving after
contact if they lock together.
16. The mass of a cannon is 500 kg. This cannon shoots shells of mass 8.0 kg. If the
muzzle velocity is 600 m/s, what is the recoil velocity of the cannon?
17. The disintegration of a plutonium atom results in two particles. One of the particles has
a mass which is 60 times larger than the other. If the larger particle's velocity is
2.3 X104 m/s [left], what is the velocity of the lighter particle?
18. a) A demented polar bear is sleeping on a horizontal ice sheet. An equally demented
hunter shoots a 0.10 kg bullet at the bear. If the speed of the bullet is 1000 m/s, and
the bear's mass is 999.9 kg, calculate how fast the bear slides after being hit.
Assume the bullet is embedded in a non vital area.
b) A smart polar bear puts on the bulletproof vest of the last hunter he had eaten. The
mass of the bear and vest is 1000 kg. This bear also goes to sleep on a horizontal
ice sheet, and is hit by a bullet from the same hunter as in part a. Because of the
vest, the bullet bounces straight back with the same speed. At what speed is the
bear sliding at, when it decides to have another meal?
19. Two identical billiard balls collide as illustrated below.
Determine ball 2's speed after collision.
20. Grain in a railway car is leaking out through a small hole in the flat bottom of the car.
The railway car is on a level straight track, and is moving with uniform velocity. If there
is no friction or any other external forces, Does the velocity of the car increase,
decrease, or remain the same? Explain!
21. A boy of mass 45 kg, while running at 4.0 m/s, jumps on a sled with a mass 15 kg, and
which is motionless on a frozen lake. Determine the velocity of the boy and sled as they
slid across the lake.
22. A truck of mass 3600 kg and a car of mass 2000 kg collide at an intersection. The
velocities of the truck and car are 10 m/s [south] and 24 m/s [east] respectively. If they
stick together after the collision, what is their velocity immediately after impact?
23. A radioisotope, initially at rest, decays by emitting an electron horizontally with
momentum 9.0 X 10-21 kgm/s [E], and a neutrino horizontally with momentum 4.8 X 10-21
kgm/s [S].
a) Determine the direction of motion of the decayed nucleus.
b) Calculate the magnitude of the momentum of the decayed nucleus.
c) Given that the mass of the decayed nucleus is 3.6 X 10-25 kg, determine its
velocity.
24. A 25.0 kg missile is ejected perpendicular to the motion of a 3000 kg space ship which
is traveling at 200 m/s. The missile moves at a speed of 2000 m/s. Determine the new
speed of the space ship, and what angle has the direction of motion changed by?
25. In order to save herself from a space rock flying towards her, an astronaut with mass
125 kg (This mass includes the mass of the equipment), pushes off from her 2500 kg
space capsule. The velocity acquired by the astronaut is 2.0 m/s. Assume that the
initial velocities of the astronaut and space capsule is 0 m/s.
a) Determine the velocity of the space capsule after she pushes off.
b) Given that she is tied to the space capsule with a 25 m rope, how long will it take
for the rope to become tight?
d) Locate the center of mass of the system when the rope becomes tight, and
determine the momentum of the center of mass.
26. When a parachutist hits the ground and comes to rest, the impact velocity is the same
as that reached by a person free falling from a height of 4.5 m.
a) Determine the impact velocity of the parachutist.
b) If the jumper has a mass of 80 kg, what impulse does the person experience?
c) What is the average force on the person's feet if
1) the jumper stops in 0.019 s because she does not bend her knees?
2) the jumper stops in 0.050 s because she bends her knees?
27. a) Determine the momentum of a girl moving at 20 m/s down a ski hill if her mass
(including equipment) is 60 kg.
b) Calculate the stopping force she experiences if she takes 3.0 s to stop as a result of
flying into deep snow.
c) How far does she go into the snow drift? Assume that the force that stops her is
constant.
28. A bullet takes 4.0 X 10-4 s to pass through a stationary block of wood. The bullet's mass
and velocity before contact is 8.0 g and 400 m/s. If the bullet emerges with a speed of
100 m/s:
a) what is the average force which caused the change in speed of the bullet?
b) what is the thickness of the wood block?
November 30. 2013
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