What Is the Final Velocity After Two Balls Collide and Move Together?

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Homework Statement

Two balls roll towards each other. Ball A moves to the right with velocity 5 m/s and ball B moves to the left with velocity 3m/s. If both balls have the same mass, m=50kg, determine the final velocity of them if they move off together after collision. In which direction will they move?

Homework Equations

F = M(Vf - Vi)/2 (is this correct?)
Vf = Vi + Acceleration * Time (is this correct?)
V = d/t

The Attempt at a Solution

M = 50kg
Vi of ball A = 5m/s
Vi of ball B = 3m/s
A = ?
T = ?

Ball A:
Vf = 5 + A * T

Using formula V = d/t
5 = d/t I stuck, don't know how to work this out. Any hints?

 

[Filip Larsen]

You need to employ conservation of momentum.