Honors Physics Collision Problems

Honors Physics Collision problems

1. A 45 kg boy runs with a horizontal velocity of 5.1 m/s off a boat dock onto a stationary 12 kg rubber raft. (a) Using conservation of momentum, find the final velocity of the boy and raft. (b) How much kinetic energy did the boy have before he hit the raft? (c) How much total kinetic energy did the boy-raft system have after the collision? (d) How much kinetic energy was gained or lost in this collision?

2. A red, 0.300 kg billiard ball is moving with a velocity of +2.00 m/s and it collides head-on (in a partially elastic collision) with a blue, 0.400 kg billiard ball moving the other way at –4.00 m/s. After the collision the red ball is moving at –0.75 m/s. (a) What is the velocity of the other ball after the collision? (b) How much kinetic energy was lost in the above collision? (Find total K.E. of each object before and after)

3. A dude and his skateboard have a total mass of 60.0 kg. He is standing at the base of a wheelchair ramp (which has a 5.00 incline, going up) getting ready to catch a bowling ball. The 9.00 kg bowling ball has a velocity of 6.20 m/s when he catches it. (a) How much kinetic energy is in the bowling ball before he catches it? (b) What is the velocity of the dude, ball, and skateboard system immediately after he catches it? (c) What is the kinetic energy of the dude, ball and skateboard immediately after the catch? (d) How far up the ramp will they roll on the frictionless skateboard? (Hint: what’s change in height? Now draw a triangle and find the length up the incline.)

4. A 5.0 g ball is fired north at a velocity of 58 m/s. It collides with a 3.5 kg ball travelling east at 65 m/s. The two balls stick and move off together at some angle to the northeast. a) Find the total combined momentum of these balls (it’s 2 dimensions, so vectors! Include the final direction in exact degrees). (b) What is their final speed?

5. A spring-loaded cannon is used to launch a 12 kg cannonball from the top of a tower, 25 meters high. To compress the spring a distance of 1.2 meter requires an average force of 860 N. (a) If the spring was compressed in 8.5 seconds, what how much power was produced? (that’s what we say, power is “produced” or “generated”). (b) After launch, determine how fast the ball should be going just before it hits the ground. (c) If the speed of the ball was measured to be only 22 m/s as it hit the ground, how many joules of heat and sound were dissipated when the ball was fired?

6. An astronaut steps out of the International Space Station to do some repairs. On her back is a jet propulsion unit. On command, a small jet of gas is ejected with a velocity of +32 m/s and the astronaut recoils with a velocity of –0.30 m/s. After the gas is ejected, the total mass of the astronaut and her suit is 160 kg. What is the total mass of the gas which was ejected?

7. A 1550 kg Lexus SUV is travelling with a velocity of 25 m/s (55 mph). The driver is talking on his cell-phone and doesn’t notice that the traffic is stopped, so he plows right into our 1120 kg rental car and our bumpers lock up and we all move along as a single unit. (a) How fast were we all (both cars) travelling immediately after the impact (before friction starts to bring us to a halt)? (b) if an average frictional force of 850 N is applied between the road and the tires, how far with the two cars skid before coming to a stop? (that is, how much work must friction do to take away all the K.E. of the two cars after the collision?)