Question

Frictional force between two bodies:
A. adds the motion between two bodies
B. opposes relative motion between contact surfaces of the bodies
C. sometimes helps and sometimes opposes the relative motion
D. increases the relative velocity between the bodies

Answer 1

In order to solve this question, we should know that Force is the agent which is the cause of change in inertia of a body either from motion to rest or brings a body from rest to motion. Here, we will discuss frictional force in brief and will figure out which option is the correct answer related to frictional force.

Complete answer:
In physics, Frictional force is defined as the force acting between the surface of contact of two bodies and this force always opposes the relative motion between the surface of contact of two bodies.For example if we put a body on some inclined surface, we notice that it begins to slide only on particular angle of inclination so the main reason the body is at rest for many angles of inclination because frictional force between body and surface contact opposes the motion and keeps body at rest and the force which is just greater than frictional force act on body it begins to slide.So, Frictional force just opposes the relative motion between surfaces of contact between two bodies.

Therefore, the correct option is B.

Note: It should be remembered that, wherever there is contact between two bodies there is frictional force, most common example is air resistance is also the kind of frictional force between surface of a body moving in air and the particles in air came in contact and hence produce air resistance which oppose the relative motion of the body.