Question

ans d
Q.28. A system of two blocks A and B are connected by an inextensible massless string as shown in the figure. The pulley is massless and frictionless. Initially the system is at rest when, a bullet of mass 'm' moving with a velocity 'u' hits the block 'B' and gets embedded into it. The impulse imparted by tension force to the block of mass 3 m is :



A) 5mu4
B) 4mu5
C) 2mu5
D) 3mu5

Answer 1

Let velocity of B and A after collision has magnitude v.

At the time of collision tension = T

Impulse provided by tension = ∫ Tdt

Consider change of momentum of (B + bullet)

mu – ∫ Tdt = 2mv     ……… (i)

Consider change of momentum A

∫ Tdt = 3mv     …………..(ii)

from (i) and (ii), mu = 5 mv

=> v = u/5

Hence, Impulse ∫ Tdt = 3mv

= 3m(u/5) = 3mu/5