# Physic question

1. Dec 27, 2009

### gold123456th

1. The problem statement, all variables and given/known data

A soft clay block is suspended so as to form a so-called ballistic pendulum. A bullet is fired point-blank into the block, imbedding itself therein and raising the latter to a height h. Derive an expression for the percentage of the kinetic energy converted into internal energy during the bullet-clay impact.

2. Relevant equations
Use any equation related to momentum and kinetic energy

3. The attempt at a solution
I managed to get an expression: (mBvB2 - mBvC2 - mCVC2)/(mBvB2) x 100
This expression is right, but I need to simplify it to (mC)/(mC + mB) x 100. I don't know how to simplify this equation
Thanks!

2. Dec 27, 2009

### rl.bhat

Use conservation of momentum and write VB in terms of VC. Substitute this in the energy equation to eliminate VC.

3. Dec 27, 2009

### gold123456th

Can you show me how to do that? I tried but had no luck

4. Dec 27, 2009

### rl.bhat

mBVB = (mB+mC)VC
Now what is VB ?

5. Dec 27, 2009

### gold123456th

i got it! thanks