A block of mass 70kg is kept on a rough horizontal surface `(mu=0.4)` . A person is trying to pull the block by applying a horizontal force, but the block is not moving. The net contact force exerted by the surface on the block is `F` , then:

Options

A. `F=700N`
B. `F=280N`
C. `700NleFle750N`
D. `F=754N`

Answer

C

Explanation

`N=70g=700N` ,
`F_(1)=muN=0.4xx700=280N`
(i) Contact force: `F=sqrt(N^(2)+f^(2))`
(ii) So `NleFlesqrt(N^(2)+f_(l)^(2))`
(iii) `700leFlesqrt(700^(2)+280^(2))` implies `700leFle754` .