Question

A box is placed on an inclined plane and has to be pushed down. The angle of inclination is:
A. Equal to the angle of friction
B. More than the angle of friction
C. Equal to the angle of repose
D. Less than the angle of repose

Answer 1

Hint:The solution to this question can be easily reach by approaching the solution as thinking what happens when the inclination is increased and decreased, also know that angle of repose is the steepest angle of descent or dip relative to the horizontal plane to which a material can be piled without slumping.

Complete step-by-step solution:
We will be trying to solve the question exactly the same as hinted in the hint section of the solution to the question. This question needs you to have conceptual understanding instead of solving some or any numerical.
Let’s first discuss the angle of repose and its meaning. Angle of repose is the steepest angle of descent or dip, relative to the horizontal plane to which a material can be piled without slumping, in other words, when the angle of inclination is equal to the angle of repose, the object that is put on the slope, it is on the verge of sliding, but just doesn’t slide yet. When the angle of inclination is more than the angle of repose, the object on the slope can slide on its own easily, on the other hand, when the angle of inclination is less than the angle of repose, we have to apply some external force to make it slide downwards.
In the question, it is clearly stated that we have to push the box to slide it downwards. Which means that the angle of inclination is actually lesser than the angle of repose.
Hence, the correct option is option (D).

Note:- Many students do not know what angle of repose is, it is the angle at which the friction acting on the object put on the slope is maximum. Some students consider the angle of friction as the max angle before the object starts to slide, which is completely wrong and unheard of.