Question

A bullet of mass0.01kg is fired with a velocity of 200m/s in to a sack of sand of mass 9.99kg which is swinging from rope .At the moment the bullet hits, the sack has a velocity of 0.2m/s. Workout the velocity of bullet and sand just after the bullet hits the sack.

Answer 1

You did not say if the sack was moving toward the rifle or away at start
initial momentum = 0.01 * 200 plus or minus 9.99 * 0.20
final momentum = (0.01 + 9.99) v
so
10 v = 2 + or - 2

Answer 2

Its correct or