Question

A 4-kg object moving 12 m/s in the positive x direction has a one-dimensional elastic collision with an object (mass = M) initially at rest. After the collision the object of unknown mass has a velocity of 6.0 m/s in the positive x direction. What is M

please need help ASAP

Answer 1

initial momentum = 4 * 12 = 48
initial Ke = (1/2) * 4 * 144 = 288

final momentum = 48 = 4 * v + M * 6 = 6 M + 4 v
final Ke = (1/2)* 4 * v^2 + (1/2) M * 36 = 2 v^2 + 18 M = 288 if perfectly elastic
v = (48 - 6 M)/4 = 12 - 1.5 M
2 (12 - 1.5 M)^2 + 18 M = 288
2(144 - 36M + 2.25M*2) + 18M = 288
288 - 72 M +4.5 M*2 + 18 M = 288
4.5 M^2 -54 M = 0
M(4.5 M -54) = 0
M = 0 or M = 54/4.5 = 12

Answer 2

thanks alottttt