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. `(5m u)/(4)`
B. `(4m u)/(5)`
C. `(2m u)/(5)`
D. `(3m u)/(5)`

Answer

D

Explanation

`-N Deltat = m(v - u), N Deltat - T Deltat = m (v - 0)`
`Tdelta = 3m(v - 0) rArr v = u//5`
`:.` Impulsive tension `Deltat = (3mu)/(5)`