Q.

Consider a body, shown in figure, consisting of two identical balls, each of mass M connected by a light rigid rod. If an impulse J=MV is imparted to the body at one of its ends, what would be its angular velocity             [2003]

1 VL  
2 2VL  
3 V3L  
4 V4L  

Ans.

(1)

Applying change in angular momentum of the system = angular impulse given to the system about the centre of mass 

(Angular momentum)f-(Angular momentum)i

       =Mv×L2=ICω             ...(i)

Here ω is the angular velocity of the rod.

Moment of Inertia of the system about its axis of rotation [centre of mass of the system]

IC=M(L2)2+M(L2)2=2ML24=ML22

 MVL2=(ML22)ωω=VL