The minimum force required to start pushing a body up a rough (frictional coefficient ) inclined plane is `F_(1)` while the minimum force needed to prevent it from sliding down is `F_(2)` if the inclined plane makes an angle`theta`with the horizontal such that `theta = 2mu` then the ratio `F_(1)//F_(2)` is :

Options

A. 1
B. 2
C. 3
D. 4

Answer

c

Explanation

Here `F_(1) = mg sin theta+ mu mg cos theta`
and `F_(2) = mg sin theta-mu mg cos theta`
`:.(F_(1))/(F_(2))=(sin theta+mucos theta)/(sin theta-mu cos theta)=(tan theta+mu)/(tan theta- mu)`=`(2mu+mu)/(2mu-mu)=(3mu)/(mu)=3`
Thus, (C) is the correct choice