Momentum physics

And I am sorry for my terrible translation.

Initial momentum is equal to zero, so is the final momentum. For the energy part use 1/2mv^2

>>7673628
My native language isn't english, please tell me what you mean about initial and final momentum :P And if I am correct you refer to P=m'*v?

If so, I can't see how P=mass f

take away the last part of that comment

How do I find v_b?

E_k*0.6=1/2*(m_a*(v_a^2)+m_b*(v_b^2))=1.44/2+3/2(*v_b^2)

>>7673650
Yes, p= m*v but you have two momentums, so [eqn] p_1 = m_1*1.2m/s = p_2 = m_2*v_2 [/eqn] Then you solve for [eqn] v_2 [/eqn] and plug it into your energy kinectic equation. And you know that the sum of the energy kinetics is only 60% of the energy of the spring.

>>7673678
I'll guess that P_a=P_b only when its a spring in the middle?

>>7673687
No, I was lazy and didn't explain that [eqn] p_a = -p_b [/eqn] since the question didn't ask for a vector so it did not matter. But it is like that because the system initially has a momentum of 0, so in the end the momentum will also be equal to 0, meaning one velocity will travel in one direction, and the other in the opposite direction. Or have a negative value in the velocity. So in any circumstance with a system that has an initial momentum of 0 the final momentum has to equal 0, this is the law of conservation of momentum. Which worded in a different way states that the initial momentum of a system must be equal to the final momentum or [eqn] p_i = p_f [/eqn] This probably doesn't make much sense to you if you have a poor understanding of english, so just google conservation of momentum.

>>7673717
It made sense, thanks.

But just to make sure, the equation for v_b will be

v_b=-m_a*v_a/m_b

>>7673725
Yep