Disc A of mass m collides with stationary disc B of mass 2m as shown in Figure.The value of coefficient of restitution for discs which the two move in perpendicular direction after collision is e. Calculate 1e.

Velocity of disc A in tangential direction isv1t=usin⁡45∘=u2 …….(1)The disc B will move along common normal direction only.Since both the discs move perpendicular to each other, so disc A should move along common tangent direction.So, vA=u2, along common tangent direction.Applying conservation of linear momentum along common normal direction, we get    mu2+0=m(0)+(2m)v2n⇒v2n=u22Hence, velocity of disc B along common normal is u22. Since, e=( Relative velocity of separation )n-line ( Relative velocity of approach )n-line ⇒ e=v2n−0ucos⁡45∘=u/22u/2=12⇒ 1e=2