Question

A block of mass $m$ is resting on a wedge of angle $\theta$ as shown in the figure. With what minimum acceleration the wedge should move so that the mass m falls freely?

• A. $g$
• B. $g\cos \theta$
• C. $g\cot \theta$
• D. $g\tan \theta$

Answer 1

The correct option is C $g\cot \theta$

When a body is in free fall, it experiences a downward acceleration of g.
Thus, the contact force between block and wedge is zero.
$a\times \sin \theta =g\times \cos \theta$
$a=g\times \cot \theta$