Solving Elastic Collisions Involving 3 Blocks

[lu22]

Homework Statement

There are 3 blocks, A B and C, arranged left to right. blocks A and C have masses of m and block B has mass of 2m. block A heads toward the other two with velocity v. determine the final velocity of each block after all subsequent collisions. assume all collisions are elastic.

Homework Equations

conservation of momentum for elastic collisions -- m₁v_i + m₂v_i = m₁v_1f + m₂v_2f

conservation of energy for elastic collisions -- 1/2m₁v_1i² + 1/2m₂v_2i² = 1/2m₁v_1f² +
1/2m₂v_1f²

The Attempt at a Solution

I tried this a couple different ways but its confusing without numbers
I also don't know if I should use just momentum or just energy or a combination of both

thanks for the help!

 

[zhermes]

You're going to have to use both conservation laws. In the end your answers should be in terms of only 'm' and the initial velocity 'v.' Start by looking at the first collision, and find the final velocities in terms of m and v. Once you have that, do the same thing for the second collision (between blocks B and C).