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

i 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

if the two bodies "stick "together after collision then the collision is inelastic,if the other one prevails then elastic