Question

A block of mass $'m'$ is placed on an inclined plane having coefficient of friction $'m'$. The plane is making an angle $\theta$ with the horizontal. The minimum value of upward force acting along the inclined plane that can just move the block up is

• A. $mg\,\cos \,\theta $
• B. $mmg\,\cos \,\theta$
• C. $ mg\,\sin\,\theta$
• D. $mmg\,\sin\,\theta$

Answer 1

Answer: (C)

Suppose a force $F$ is acting on the block as shown in the figure.
Minimum value of the force required to just move the block up is
$F_{\min }=m g \sin \theta+f_{\min }$
Where, $f =$ frictional force $f_{\min }=0$
$\Rightarrow F_{\min }=m g \sin \theta$