A small block of mass of `0.1 kg` lies on a fixed inclined plane `PQ` which makes an angle `theta` with the horizontal. A horizontal force of `1N` acts on the block through its centre of mass as shown in the figure. The block remains stationary if ( take `g=10 m//s^(2))`

Options

A. `(i) ,(ii)`
B. `(i) ,(iii)`
C. `(i) ,(iv)`
D. `(ii),(iv)`

Answer

B

Explanation

The block remains stationary.
(i) If ` sin theta = cos theta , i.e. theta = 45^(@)` , no need of friction to develop
(iii) If `theta gt 45^(@)`
`sin theta gt cos theta , friction will act along `Q` to keep the block at rest
`sin theta = cos theta + f`
`(iv) If `theta lt 45^(@)`
`sin theta lt cos theta` , friction will act along `p`
`(i)` and `(iii)` are correct.