A stone of 1 kg tied up with 10/3 m long string rotated in a vertical circle. If the ratio of maximum and minimum tension in string is 4 then speed of stone at highest point of circular path will be ( `g = 10 ms^2)`

Options

A. `10ms^(-1)`
B. `5sqrt2ms^(-1)`
C. `10sqrt3ms^(-1)`
D. `20ms^(-1)`

Answer

A

Explanation

Minimum tension is at topmost point (speed = v) and maximum tension at bottommost point (speed = u).
`(T_(max))/(T_(min))=(mg+(m u^(2))/(L))/(-mg+(mv^(2))/(L))=4`
`u^(2)=v^(2)+2g(2L)`
Solving, we get `v=10ms^(-1)`