# Thread: a physics questions really teasing me

1. ## a physics questions really teasing me

its the part b that i need help in . well i tried to solve it but failed to do so i arrived to equation v= V-u but cant go any furthur as after i plug this in v^2 things get quite complicated

2. ## Re: a physics questions really teasing me

So did you get the equations right in part a? I'll assume you did.

Rearranging them a little gives:

$u-v=\frac{M}{m}V$

and

$u^2-v^2=\frac{M}{m}V^2$

Factorise the left side of the second equation and everything will become easy.

3. ## Re: a physics questions really teasing me

i didnt actually get it can u please elaborate it a little thanks

4. ## Re: a physics questions really teasing me

$a^2-b^2=(a+b)(a-b)$

5. ## Re: a physics questions really teasing me

this is how i solve can u point out at what am i doing wrong
v=V-u equation 2
mv+MV=mu equation 1
multiplying eq 2 by M
we get Mv=MV+Mu equation 3
adding equation 3 and 1 we get
v=(m-M)u/(m+M) equation 4
multiplying eq 2 by m
mv=mV-mu equation 5
adding equation 5 and 1 we get
V=2mu/(m+M)
plugging these values in the energy loss in kinectic energy
mu^2{1-(m+M)2-4mM/(m+M)^2 i get 0/(m+M)^2 i know i am close but what i am doing wrong??