# Homework Help: Kinetic Energy Exploding Question

1. Oct 21, 2007

### shell4987

1. The problem statement, all variables and given/known data
An object, with mass 79 kg and speed 23 m/s relative to an observer, explodes into two pieces, one 5 times as massive as the other; the explosion takes place in deep space. The less massive piece stops relative to the observer. How much kinetic energy is added to the system during the explosion, as measured in the observer's reference frame?

2. Relevant equations
KE=1/2mv^2

3. The attempt at a solution

Since I have two masses, I don't know where to start on this problem. Any suggestions?

2. Oct 21, 2007

### G01

Eventually the kinetic energy formula will come into play here, but during the explosion energy is NOT conserved, since it tells us the explosion adds energy. But can you tell me what is conserved in the explosion?

3. Oct 21, 2007

### shell4987

Mass is conserved in this explosion but it's in two different forms.

4. Oct 21, 2007

### G01

Anything else?

5. Oct 21, 2007

### shell4987

Momentum?

6. Oct 21, 2007

### G01

Yup!

Now using momentum, can you find find the final energy of both masses?

If you can, then it is just a matter of finding the difference between the initial and final energy.