A particle is rotated in a vertical circle by connecting it to a string of length `l` and keeping the other end of the string fixed. The minimum speed of the particle when the string is horizontal for which the particle will complete the circle is

Options

A. `sqrtgl`
B. `sqrt2 gl`
C. `sqrt3 gl`
D. none

Answer

B

Explanation

`(1)/(2)m v^(2) + mgl = (1)/(2)m u^(2)`
For `u_(min) = v = 0 :. u_(min) = sqrt(2gl)`