A block of mass 2kg rests on a rough inclined plane making an angle of `30^@` with the horizontal. The coefficient of static friction between the block and the plane is 0.7. The frictional force on the block is

Options

A. 9.8 N
B. `0.7xx9.8xxsqrt(3) N`
C. `9.8xxsqrt(3) N`
D. `0.7xx9.8 N`

Answer

A

Explanation

(a) Angle of respose `theta_(r)=tan ^(-1)(mu_(s))=tan^(-1)(0.7)`
or `tan theta_(r)=0.7`
Angle of plane is `theta=30^(@), tan theta= tan 30^(@)=0.577`
Since`" " tan theta lt tan theta_(r), theta lt theta_(r)`
Block will not slide or `f= mg sin theta ne mu mg cos theta`
or `" " f=(2)(9.8) sin 30^(@)=9.8 N`