Q.

A particle of mass m moving with velocity v collides with a stationary particle of mass 2m. After collision, they stick together and continue to move together with velocity ______.         [2023]

1 v  
2 v2  
3 v3  
4 v4  

Ans.

(3)

Applying conservation of linear momentum

⇒P→i=P→f

mv+2m×0=(3m)v'

∴   mv=3mv' ⇒ v'=v3