Question

A 6.4-N object is traveling at 9.9 m/s. It strikes an 2.1-N object, which is stationary. The two objects stick together. Their common final speed is:

Answer 1

M1*V1 + M2*V2 = M1*V + M2*V.
6.4*9.9 + 2.1*0 = 6.4V + 2.1V.

Solve for V.