Two smooth block are placed at a smooth corner as shown in fig. Both the bloks are having mass m. We apply a force F on the block m. Block A presses block B in the normal direction, due to which pressing force on vertical wall will increase, and pressing force on the horizontal wall decreases, as we increases `F(theta = 37^(@)` with horizontal).

As soon as the pressing force on the horizontal wall by block B become zero, it will lose contact with ground. If the value of F further increases, block B will accelerate in the upward direction and simulaneously block A will towards right.
What is the minimum value of F to lift block B from ground?

Options

A. `(25)/(12)mg`
B. `(5)/(4)mg`
C. `(3)/(4)mg`
D. `(4)/(3)mg`

Answer

C

Explanation

For `equli.` of block `(A)`
`F=N sin theta`
`N=F//sin theta`
To lift block `B` from ground
`N cos theta ge mg`
`(F)/(sin theta ) cos theta ge mg`
`Fgemg tan theta=mg((3)/(4))`
So, `F_(mi n)=(3)/(4) mg`