# Homework Help: What fraction of the kinetic energy is converted to other forms in collision?

1. Jul 31, 2012

### dawn_pingpong

1. The problem statement, all variables and given/known data
there are 2 blocks along a frictionless track. block 1 has a mass of m1 and block 2 has a mass of m2. Block 1 is initially moving at a speed of v0. it collides and sticks to the initial stationary block 2. (m2=9m1) what fraction of the inital kinetic energ of the system is converted to other forms (heat, sound...) as a result of the collision?

1)1%
2)10%
3)50%
4)90%
5)95%

2. Relevant equations
I sort of think this as more of a general knowledge question... this is the 2nd part. the first part ask you to calculate the velocity after collision

3. The attempt at a solution

2. Jul 31, 2012

### voko

The figure out part 2, you need to solve part 1.

3. Jul 31, 2012

### dawn_pingpong

the answer to part 1 is 1/10v0, if I'm not wrong. Used momentum formula.

4. Jul 31, 2012

### voko

Correct. Now you just need to compute the total kinetic energies before and after the collision, and compare them.

5. Jul 31, 2012

### dawn_pingpong

yay yay thank you!

initial:final=1 x v^2 : 10 x (0.1v)^2=1:0.1
so 90% of KE was converted to other forms! Thank you once again:D