A short boy sits on a seat suspended by a light string from a fixed point O and starts swinging in a vertical plane from the extreme position P with a small amplitude the graph which shows the variation of the tension in the string with time 't' is:

Options

A.
B.
C.
D.

Answer

C

Explanation

`T-mgcostheta= (mv^(2))/l costhetaapprox 1-theta^(2)/2`
`T=mgcostheta+(mv^(2))/(l) v= l r=l theta_(0) omega cos (omegat +phi)`
`=mg+ml theta _(0)^(2)omega^(2)cos^(2)(omegat+phi)-(mg)/2 theta_(0)^(2)sin^(2)(omegat+phi)`
`Rightarrow T_(max)` at mean and is never 0 Rightarrow (C)