Question

As an inclined plane is made slowly horizontal by reducing the value of angle $\theta$ with horizontal, the component of weight parallel to the plane of a block resting on the inclined plane:

• A. decreases
• B. remains same
• C. increases
• D. increases if the plane is smooth

Answer 1

The correct option is A decreases

For rough surface,
Weight component parallel to the plane $W_r=mg\sin \theta -\mu mg\cos \theta$
As $\theta$ deceases so $\sin \theta$ will decrease and $\cos \theta$ will increase. Thus, $W_r$ will decrease.
For smooth surface, parallel force to the plane $W_s=mg\sin \theta$
As $\theta$ deceases so $\sin \theta$ will decrease and also $W_s$ will decrease.
Thus, weight component parallel to the plane will always decrease when $\theta$ decreases.