Momentum Practice Probiems A 20 kg tennis ball launcher shoots a 0.057 kg tennis

Question

Momentum Practice Probiems A 20 kg tennis ball launcher shoots a 0.057 kg tennis ball across a frictionless court. If the tennis ball's velocity after it is launched is 36 m/s to the north, what is the velocity of the tennis ball launcher? 1. A 0.008 kg bullet going 400 m/s to the east hits a tin can filled with sand (total mass 5 kg) and gets stuck inside in an inelastic collision. Assuming there is no friction, how fast is the can (and the bullet) moving after the collision? 2. A 110 kg running back carries the ball south at 8 m/s. A 130 kg linebacker runs to make the tackle going north at 5 m/s. In their collision, the linebacker wraps his arms around the runner and makes it an inelastic collision. How fast are they moving right after the collision (before they fall to the ground)? 3. A 2000 kg SUV traveling at 7 m/s south runs into the rear end of an 800 kg compact car sitting at a stop light in an elastic collision. If the compact car is going forward at 7 m/s right after the collision, how fast is the SUV traveling? 4. Beaker and Honeydew are driving bumper cars. They spot each other across the rink and head straight for each other at full speed. Honeydew and his car (130 kg total) head east at 3.5 m/s while Beaker and his car (110 kg total) head west at 3.0 m/s. They have an elastic collision when they meet and Honeydew (and car) bounces backwards at 2.4 m/s. What is Beaker's speed after the collision? 5. The cue ball going 9 m/s heads directly toward a 0.17 kg object ball at rest near the pocket. During the elastic collision, the cue ball stops and the object ball is launched forward at 9 m/s. What is the cue ball's mass? 6.

Explanation / Answer

Q1.

using conservation of momentum principle:

momentum before =momentum after

as both the launcher and the tennis ball were at rest before the launch, momentum before =0

let velocity of the launcher after launch is v m/s.

then momentum after=0.057*36+20*v

where north is considered positive direction

using conservation of momentum principle:

0.057*36+20*v=0

==>v=-0.057*36/20=-0.1026 m/s

hence the speed is 0.1026 m/s and in south direction.

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