The coefficient of friction between the block and the horizontal surface is mu. The block moves toward right under action of horizontal force `F` (figure-a). Sometime later another force `P` is applied to the block making an angle theta `(such that tan theta=mu)` with vertical as shown in (figure-b). After application of force `P` , the acceleration of block shall.

Options

A. Increases
B. Decrease
C. remains same
D. information insufficient for drawing inference.

Answer

C

Explanation

The free body diagram of block in fig. `b` is as shown.
:. `N=mg+Pcostheta`
and acceleration of block
`a=(F+P sintheta-mu(mg+Pcoshtheta))/(m)`
`a=(F+P sintheta-(sintheta)/(costheta)(mg+Pcoshtheta))/(m)=(F-mumg)/(m)` Hence `P` does not change acceleration.