A block of mass m is placed on an inclined plane with angle of inclination `theta` let N, `f_(L)` and F respectively represent the normal reaction limiting force of frcition and the net force down the inclined plane. Let `mu` be the coefficient of friction. the variations of N, `f_(L)` and F with `theta` is indicated by plotting graphs as shown its figure. Then, curves 1,2 and 3 respectively represent.

Options

A. N,F and `f_(L)`
B. `F, f_(L) and N`
C. `F,N and f_(L)`
D. `f_(L),N and F`

Answer

C

Explanation

The normal reaction `N=(mg cos theta)` and the frictional force `f_(L)=(=mu mg cos theta)` vary as cosine of the angle of inclination `theta`. The net downward force after friction attains it limiting value is given by `(mg sin theta-mu mg cos theta)`. Note that the downward force is zero up to the angle of repose, i.e., till the friction force has not attained its limiting value.