Question
One meter long elastic wire is fixed at one end and at the other end a weight of 3kg is attached. The mass is pulled away from vertical line (passing through point of suspension) to a distance 0.6m and made to revolve with horizontal circle of radius 0-6m. Find the increase in length of the wire. Given that area of cross-section of wire 2x10–7m2 and Young's modulus of material of wire 2.5x1010 N/m2.
Solution
The given question is illustrated in the figure. below.
From right angled 
,
The different forces acting on mass are:
(i) Weight mg in vertically downward direction.
(ii) Tension T in the string along AS.
Now resolving the components of T as shown in fig. above.
The component Tcosθ balances the weight mg of the mass and component Tsinθ provides the necessary centripetal force to whirl the mass.
