Question

A ball B₁ of mass M is moving with velocity ν along north. It collides with another Ball B₂ of same mass moving with velocity ν along east. After the collisions both balls stick together and move along north east. What will be the velocity of the combination.

(A) ν 

(B) 2ν 

(C) √2ν 

(D) ν/√2 

Answer 1

Answer is (D) ν/√2

Let the velocity of the combination be V, then

momentum of combination along north = momentum of ball initially moving along north.

That is 2 MV cos45° = Mν. 

Which gives V =ν/√2.