Question
A pendulum made of a uniform wire of cross-sectional area A has time period T. When an additional mass M is added to its Bob, the time period changes TM. If Young's modulus of the material of the wire is Y, then 1/Y is equal to (g = gravitational acceleration)
Solution
A.
Time period, 
When additional mass M is added to its Bob
where Δ is increase in length
As we know that,
