Question

In the bloodstream, an erythrocyte (red blood cell) of mass m moves with velocity v to the right. Ir collides head-on with a leukocyte (white blood cell) of twice its mass moving to the left with three times its speed. After the collision, the became stuck together. What would the final velocity be of the combined cells after the collision in terms or f v?

Answer 1

initial momentum right = m v - 2m*3v
= -5 m v

final momentum the same
final mass = 3 m
so
3 m Vfinal = - 5 m v

Vfinal = - (5/3) v