Two blocks A and B of masses m and 2 m are connected by a massless spring of force constant k and are placed…

Two blocks A and B of masses m and 2m are connected by a massless spring of force constant k and are placed on a smooth horizontal plane. The spring is stretched by an amount x and then released. The relative velocity of the blocks when the spring comes to its natural length is

  1. x3k2m
  2. x2k3m
  3. xk3m
  4. x2km

Solution

Let us assume the velocity of block A and B are v1 and v2 respectively.

Relative velocity will be v1+v2

Using conservation of linear momentum

mv1=2mv2

   v1=2v2

Using conservation of energy

12kx2=12mv12+122mv22

12kx2=12m2v22+mv22

12kx2=2mv22+mv22

3mv22=kx22

v22=kx26m

v2 k6m.x

Relative velocity =3v2

=3k6m.x

= 3k2m.x

Asked in: Practice

Practice more Center of Mass Momentum and Collision questions on Aicharya