## Monday, September 27, 2010

### Momentum, momentum conservation and impulse

Questions

1).A boy hits a 0.05-kg golf ball, giving it a speed of 75 m/sec.What impulse did he deliver to the ball? If the duration of impact is 0.01 seconds, what was the average force of impact?

2)During an automobile crash test, a 1000 kg car is sent towards a cement wall at a speed of 14 m/sec and is brought to a stop in 0.08 seconds. What was the average force of the car on the wall?

3)Two children, totaling 200 kg, are traveling at 10 m/sec in a 100-kg bumper car during an amusement park ride. They deliberately collide with an empty second car, mass 100 kg, which is at rest. Afterwords, the car with the two children moves off at a speed of 4.0 m/sec. What is the final velocity of the empty car?

4)James, a 65-kg skin diver, shoots a 2.0-kg spear with a speed of 15 m/sec at a fish which is darting past him. How fast does James recoil when the spear is initially released?

5)Running at 2 m/sec, Jack, the 45-kg quarterback, collides with Leon, the 90-kg tackle, who is traveling towards him at 7.0 m/sec. Upon colliding, Leon continues to travel forward towards Jack, at 1.0 m/sec. How fast is Jack knocked backwards?

6)A 620-kg moose stands in the middle of the railroad tracks in Sweden, frozen by the lights of an oncoming 10,000-kg locomotive traveling at 10 m/sec. Even though the engineer attempted in vain to slow the train down in time to avoid hitting the moose, the moose rides down the remaining track sitting on the locomotive's cowcatcher. What is the final velocity of the locomotive and moose after the collision?

7)On a hot summer day, Jack and Leon are fishing in their boat, when they decide to jump into the water to cool off. Jack, 45-kg, jumps off the front of the boat with a speed of 2 m/sec. While at the exact same moment, Leon, 90-kg, jumps out of the back of the boat at a speed of 4 m/sec. If the boat has a mass of 100 kg and was at rest prior to the two boys jumping off, what will be its velocity just after both boys have abandoned ship?

8)A 5.0 kg boy runs at a speed of 10.0m/s and jumps onto a cart. The cart is initially at rest. If the speed, with the boy on the cart, is 2.50 m/s, what is the mass of the cart?

9)Assuming no water resistance, a big fish is gliding through the water with momentum 2.0kg m/s. It swallowed a small fish of mass 200g, moving in the opposite direction at a very fast speed of 17m/s relative to the big fish. As a result of that, the big fish felt a punch in his stomach and regretted his move. The mass of the big fish is 1kg .What was the final velocity of the big fish after the meal?

10)A wooden block of 1 kg is at rest. A metal bullet of speed 500m/s and mass 10g was embedded in the wooden block upon impact. A second bullet, having the same mass and speed as the first one , but made of rubber, bounced back with speed of 200m/s upon impact with the same wooden block.

i) Which bullet has undergone a greater change in momentum? Please show your workings.

ii) What is the final kinetic energy of the bullet-block system in each case?

11) A 2.5 kg ball and a 5.0 kg ball have an elastic collision. The 2.5 kg ball was at rest and the other ball had a speed of 3.5 m/s. What is the kinetic energy of the 2.5 kg ball after the collision?