Question

A 0.030-kg ball moving eastward collides with a 0.006-kg ball moving along the same line with a velocity of 20 m/s eastward. After collision, the 0.030-kg ball attains a velocity of 27 m/s eastward. What is the velocity of the 0.001 -kg ball?

Answer 1

conserve momentum. If we consider eastward as positive, then
0.030*v1 + 0.006*20 = 0.030*27 + 0.006*v2
I see two problems here
(a) where the heck did the 0.001-kg ball come from?
(b) v2 can only be determined in terms of v1, which is unknown.