After perfectly inelastic collision between two identical particles moving with same speed in different directions, the speed of the particles become half the initial speed. Find the angle between the two before collision.

Explanation

Linear momentum remains conserved.
Resultant initial momentum,
`p=sqrt(p_(1)^(2)+p_(2)^(2)+2p_(1)p_(2)costheta)`
`{2m((v)/(2))}^(2)={mv}^(2)+{mv}^(2)+2{mv}{mv}costheta`
`1=1+1+2xx1xx1costheta`
`2costheta=1-2`
`costheta=-(1)/(2)`
Angle `theta=120^(@)`