In a physics lab, 0.30 kg puck A, moving at 5.0 m/s [W], undergoes a collision with 0.40 kg puck B, which is initially at rest. Puck A moves off at 4.2 m/s [W 30° N]. Find the final velocity of puck B.

Answer 1

conserve momentum.
0.30<-5,0> = 0.30<-3.63,2.1> + 0.40<vx,vy>
solve for vx,vy the components of puck B's velocity

Answer 2

Given: M1 = 0.30 kg, V1 = -5.0 m/s.
M2 = 0.40 kg, V2 = 0.
V3 = 4.2 m/s[150o] CCW = velocity of M1 after collision.
V4 = velocity of M2 after collision.

M1*V1+M2*V2 = M1*V3+M2*V4.
0.30*(-5)+0.40*0 = 0.30*4.2[150o]+0.40*V4
-1.50 = 1.26[150o]+0.40*V4
-1.5 = -1.09+0.63i + 0.4*V4
-0.4*V4 = 0.41+0.63i
V4 = -1.025-1.575i = 1.88m/s[57o] S. of W. = velocity of puck B.