A system of two blocks `A` and `B` are connected by an inextensible massless string as shown in Fig. The pulley is massless and frictionless. Initially, the system is at rest. A bullet of mass `m` moving with a velocity `u` as shown hits block If and gets embedded into it. The impulse imparted by tension force to the block of mass `3m` is

Options

A. `(5"mu")/4`
B. `(4"mu")/5`
C. `(2"mu")/5`
D. `(3"mu")/5`

Answer

D

Explanation

By conservation of linear momentum along the string `"mu"=(m+m+3m)v` or `v=u/5`
and impulse on block `a=3m(v-0)=(3mu)/5`