A stone of mass `m` is tied to a string and is moved in a vertical circle of radius `r` making `n` revolution per minute. The total tension in the string when the stone is its lowest point is.

Options

A. mg
B. `m(g + pi nr^(2))`
C. `m(g + npir)`
D. `m{g +(pi^(2)n^(2)r)//900}`

Answer

D

Explanation

Tension at lowest point
`T_("max") = (mv^(2))/r + mg = momega^(2)r + mg`
` = m[g + (2pif)^(2) r]`
`= m[g + 4pi^(2) n^(2)/(60)^(2) .r] = m[g + (pi^(2)n^(2)r)/900]`