If in the previous problem, the breaking strength of the string is `2mg`, then the minimum tension in the string will be

Options

A. `mg`
B. `(mg)/(4)`
C. `(3mg)/(4)`
D. `(mg)/(2)`

Answer

D

Explanation

At the lowest point ,`T=2mg`
`T-mg=(mv^(2))/(l)impliesv=sqrt(gL)`
`v'^(2)=v^(2)-2gL(1-costheta)`
`0=gL-2hL(1-costheta)`
`cos theta=(1)/(2)impliestheta=60^(@)`
`T'-mg cos theta=(mv'^(2))/(L)=0`
`T'-mg cos 60^(@)impliesT'=(mg)/(2)`