# What is (KE1-KE2)/KE2=M/(M+m)

1. Nov 7, 2005

### priyavyas13

hi i have a question. What does this equation mean??
(KE1-KE2)/KE2=M/(M+m) and how is it derived??

2. Nov 7, 2005

### dimensionless

Could you give more information? For instance does this have anything to do with planets, pendulums, levers, or pullies?

3. Nov 7, 2005

### rho

What does M and m represent? Is this molecular kinetic theory? (i.e. M is mass of volume V of gas and m is the mass of one molecule) or is it mechanics?

Last edited: Nov 7, 2005
4. Nov 7, 2005

### priyavyas13

heyy...sorry

the question has to do with collision..the conservation of energy and momentum. the formula has to do with the theoretical fractional energy loss
the letters "f" and "i" are subscript. (KEi-KEf)/KEi=M(M+m)
It looks like you have two objects in a system and this systme has an initial kinetic energy of $$KE_i$$ and a final kinetic energy of $$KE_f$$. When v<<c, $$KE= \frac{1}{2}mv^2$$. When v is not v<<c then $$KE= \frac{mc^2}{\sqrt{1-v^2/c^2}}-mc^2$$.