Help elastic head-on collision

[snowbelle]

a 3.42g object moving to the right at 16.4 cm/s makes an elastic head-on collision with a 6.84g object that is initially at rest. find the velocity of the first object immediately after collision. Answer in units of cm/s. What fraction of the initial kinetic energy is transferred to the 6.84g object?

I don't understand how to do this problem. I think for the first part is it
M1v1i+M2V2i=M1V1f+M2V2f
and I am lost after that. I completely don't get part 2

 

[NateTG]

Indeed, you have:
[tex]P_{\rm{initial}}=P_{\rm{final}}[/itex]
which gives you one equation.

But, you have two unknowns ($v_1$ and $v_2$), so you'll need another equation. What do you know about elastic collisions?

 

[snowbelle]

energy and momentum is conserved in elastic collisions?

 

[NateTG]

energy and momentum is conserved in elastic collisions?

Right. The equation you have listed only deals with momentum.

 

[snowbelle]

hmm i still don't get it

 

[NateTG]

hmm i still don't get it

Can you write expressions for the total kinetic energy before and after the collision?