Question

Which of the following is a self-adjusted force?
(A) sliding friction
(B) static friction
(C) limiting friction
(D) dynamic friction

Answer 1

Hint
We know that friction is a force which comes into play to resist the motion or this attempt. We will then write what is static friction. Static friction helps a body to remain this body stationary. We know that if the applied force exceeds the maximum limit the block no longer is at rest. So static friction is a self-adjusting force.

Complete step by step answer
We know that friction is a force which opposes relative motion or tendency of relative motion between two surfaces in contact.
For a pair of surfaces in contact with each other, if a futile attempt is made to slide one of those, then the force developed to resist the relative motion is called static friction.
Suppose we are pushing a block placed on a rough surface. It does not move. The force we are providing is exactly equal to the frictional force provided by the surface. If the applied force is increased the frictional force also increases automatically to balance it. The block remains at rest. The static frictional force by itself increases by the exact amount required to balance the applied force, before the motion starts. This happens until the frictional force value reaches its maximum.
Hence, before any relative motion between the surfaces begins, the frictional force is a self-adjusting force.
Static friction is considered a self-adjusting force because it wants the objects to remain at rest and not move.
Hence the required solution is static friction (option – ‘B’).

Note
Kinetic friction is not self-adjusting force because static friction becomes kinetic or sliding friction and the object begins to move. So, option ‘A’ will not be correct. The maximum possible magnitude of static friction is called limiting friction. If the force applied exceeds this limit. It no longer remains stationary. So, option- ‘C’ is also not correct.