A block of mass m is placed on a rough plane inclined at an angle `theta` with the horizontal. The coefficient of friction between the block and inclined plane is `mu` . If`theta lt tan^(-1) (mu)` , then net contact force exerted by the plane on the block is :

Options

A. mg cos `theta`
B. mg
C. mg sin `theta`
D. None of these

Answer

B

Explanation

Since `theta lt tan^(-1) mu`, block doesn't slide on the incline
`:. F = m g sin theta` `N = m g cos theta`
Net contact force, `R = sqrt(N^(2) + f^(2)) = mg`