Kinetic Energy Exploding Question

[shell4987]

Homework Statement

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?

Homework Equations

KE=1/2mv^2

The Attempt at a Solution

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

 

[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?

 

[shell4987]

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?

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

 

[G01]

Anything else?

 

[shell4987]

Anything else?

Momentum?

 

[G01]

Momentum?

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.