A rectangular box lies on a rough inclined surface The co-efficient of friction beteen the surface and the box is `mu`. Le the mass of the box ne m What is the force acting on the box down the plane if the angle of inclination of the plane is increased to `alpha gt theta` ? .

Options

A. `mg (S "in" alpha + mu "Cos" alpha)`
B. `mg C os theta`
C. `mg ("Sin" alpha - mu "Cos" alpha)`
D. `mg "Sin" theta + f`

Answer

C

Explanation

When angle of incliantion is increased to `alpha gt theta` then net force acting on the box, down the plane is
`F_(1) =mg sin alpha f =mg "sin" alpha -muN`
`=mg ("sin" alpha -mu "cos" alpha)`
.