Question

If the man wants to move the block up the incline, what minimum force is required to start the motion?

• A. $\frac{2}{3}mg$
• B. $\frac{mg}{2}$
• C. $\frac{7mg}{6}$
• D. $\frac{5mg}{6}$

Answer 1

The correct option is C $\frac{7mg}{6}$

When the man wants to move the block up, the friction starts to act down the incline in addition to the downward weight and force $F$.

Thus $F^{\prime }=mgsin\theta +\mu mgcos\theta$

$⟹F^{\prime }=\frac{mg}{2}+\frac{4}{3\sqrt{3}}mg\frac{\sqrt{3}}{2}$

$=\frac{7mg}{6}$