A(n) 19 g object moving to the right at

Question

39 cm/s overtakes and collides elastically with
a 36 g object moving in the same direction at
19 cm/s.
Find the velocity of faster object after the
collision.
Answer in units of cm/s.

(I know this is a lot similar to another problem that shows how to find the velocity of the slower object, but when finding the velocity of the faster object, do you solve the same way, if not, then how do you solve to get the velocity of the faster object?)

Answer 1

Given: M1 = 19 g, V1 = 39 cm/s.
M2 = 36 g, V2 = 19 cm/s.
V3 = velocity of M1 after collision.

V3 = ((M1-M2)V1 + 2M2*V2)/(M1+M2)
V3 = (-17*39 + 72*19)/55 = 705/55 = 12.8 cm/s.