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## Homework Statement

Hi guys, I have a few physics problems that I have no clue on how to solve. I'm not really good at kinetic and potential energy and I would like some help on these problems. Here they are:

1.) A block starts from rest at the top of a 31.0 in inclined plane and encounters a spring, of constant 3.4 N/m, rigidly attached to the plane. if the block's mass is 33.0 kg and it compresses the spring by 37.0 cm, find the distance the block travelled before it encountered the spring.

2.) A child throws a tennis ball at 12 m/s directly at the front of a school bus which is moving at 21 m/s towards him. if the collision is elastic, find the speed with which the ball bounces from the bus.

3.) An object initially at rest explodes in two fragments of masses 4.3 kg and 1.6 kg that move in diametrically opposite directions. if the speed of the first fragment is 8.4 m/s, find the internal energy of the explosion. (WTF??!)

4.) An object initially at rest explodes in two fragments of masses 4.3 kg and 1.6 kg that move in diametrically opposite dirrections. if the speed of the first fragment is 8.4 m/s, find the internal energy of the explosion.

Okay, so I have NO CLUE where to start on these problems. You don't have to work out all these problems, but 1 would be helpful. Note, I'm NOT asking for the answers. But I am asking how to start or solve the problems so that I could know how to solve them in the future. Please help me guys! i really appreciate it.

## Homework Equations

PE=mgh??

KE=1/2mv^2

(that's all I really understand....smh)

## The Attempt at a Solution

I've tried to attempt....but i've got nothing......not working AT ALL..