# Conservation of Momentum. Collisions Problems

```Name _______________________________________ Mods ____________ Date _______________
Momentum Conservation and Collisions Problems
1. Two cars collide on a gravel roadway on which frictional forces are large. Is it isolated system? If
no, then what is the external force?
2. Two air track gliders collide on a friction-free air track. Is it isolated system? If no, what is the
external force?
Collisions
pbefore = pafter
m1*v1 + m2*v2 = m1*v1f + m2*v2f (elastic collision)
m1*v1 + m2*v2 = (m1 + m2)*v2f (inelastic collision)
Please solve the following problems using all problem solving steps:
1.
2.
3.
4.
Draw a sketch and label variables.
Write the formula.
Substitute numbers and calculation.
3.
A 15-kg medicine ball is thrown at a velocity of 20 km/hr to a 60-kg person who is at rest on ice.
The person catches the ball and subsequently slides with the ball across the ice. Determine the
velocity of the person and the ball after the collision.
4.
A 0.150-kg baseball moving at a speed of 45.0 m/s crosses the plate and strikes the 0.250-kg
catcher's mitt (originally at rest). The catcher's mitt immediately recoils backwards (at the same
speed as the ball) before the catcher applies an external force to stop its momentum. If the
catcher's hand is in a relaxed state at the time of the collision, it can be assumed that no net
external force exists and the law of momentum conservation applies to the baseball-catcher's mitt
collision. Determine the post-collision velocity of the mitt and ball.
5.
A 3000-kg truck moving with a velocity of 10 m/s hits a 1000-kg parked car. The impact causes the
1000-kg car to be set in motion at 15 m/s. Assuming that momentum is conserved during the
collision, determine the velocity of the truck immediately after the collision.
6.
Suppose that you have joined NASA and are enjoying your first space walk. You are outside the
space shuttle when your fellow astronaut of approximately equal mass is moving towards you at 2
m/s (with respect to the shuttle). If she collides with you and holds onto you, then how fast (with
respect to the shuttle do you both move after the collision?
7.
A large fish is in motion at 2 m/s when it encounters a smaller fish that is at rest. The large fish
swallows the smaller fish and continues in motion at a reduced speed. If the large fish has three
times the mass of the smaller fish, then what is the speed of the large fish (and the smaller fish)
after the collision?
8.
A 25.0-gram bullet enters a 2.35-kg watermelon and embeds itself in the melon. The melon is
immediately set into motion with a speed of 3.82 m/s. The bullet remains lodged inside the melon.
What was the entry speed of the bullet? (CAUTION: Be careful of the units on mass.)
9.
A 25.0-gram bullet enters a 2.35-kg watermelon with a speed of 217 m/s and exits the opposite
side with a speed of 109 m/s. If the melon was originally at rest, then what speed will it have as the
bullet leaves its opposite side? (CAUTION: Be careful of the units on mass.)
10.
In a physics lab, a 0.500-kg cart (Cart A) moving with a speed of 129 cm/s encounters a collision
with a 1.50-kg cart (Cart B) that is initially at rest. The 0.500-kg cart rebounds with a speed of 45
cm/s in the opposite direction. Determine the post-collision speed of the 1.50-kg cart.
11.
A 3000-kg truck moving rightward with a speed of 5 km/hr collides head-on with a 1000-kg car
moving leftward with a speed of 10 km/hr. The two vehicles stick together and move with the same
velocity after the collision. Determine the post-collision velocity of the car and truck. (CAREFUL: Be
cautious of the +/- sign on the velocity of the two vehicles.)
12.
During a goal-line stand, a 75-kg fullback moving eastward with a speed of 8 m/s collides head-on
with a 100-kg lineman moving westward with a speed of 4 m/s. The two players collide and stick
together, moving at the same velocity after the collision. Determine the post-collision velocity of the
two players. (CAREFUL: Be cautious of the +/- sign on the velocity of the two players.)
```