a proton (mass 1.67 *10^(-27) kg) is moving at 1.25 *10^(-6)m/s directly toward a stationary helium nucleus (mass 6.64 *10^(-27) kg). After the head on collisions, what is the proton and helium's velocity?

Question

a proton (mass 1.67 *10^(-27) kg) is moving at 1.25 *10^(-6)m/s  directly toward a stationary helium nucleus (mass 6.64 *10^(-27) kg). After the head on collisions, what is the proton and helium's velocity?

anonymous · Answer

know that m1= Proton kg, m2=Helium kg, v1intial= 1.25 *10^(-6) m/s, and v2intial=0m/s. 
and also, i think you use this equation p1=p2

anonymous · Answer

how can you find the proton's velocity when you have two velocity unknown?
And can you guy help explain how you can indicate this problem is inelastic or elastic.

anonymous · Answer

this should be an elastic one as it si collisions of 2 DIFFERENT species(remeber alpha sctter experiment)if it collides and bounces back it shud be elastic collision...
use kinectic energy conservation
and momentum conservation
get 2 equations with v1 and v2 and solve for them