When a body B moves with a body A kept over it, then force of friction for body A is in direction of motion of A, and force of friction of body B is in direction opposite to direction of motion. Please explain this with diagrams if possible.

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FRICTN BASCLLY OPPOSES RELATVE MOTION BETWN 2 BODIES IN CONTCT. THS BSC DEFINTN OF FRCTN CLEARS ALL DIRECTNS. C NW FOR BODY B ITS MOVNG FWD CZ OF WTEVR FORCE,IT HAS TENDENCY TO MOVE FWD. THERE R 2 SURFACES IN CONTCT WID IT-ground nd body A. these 2 bodies will apply frictnal force on it in such way that it opposes relatv motn betwn them nd moving body B. SO friction on body b is in bckwddrctn trying to stop its relative motn.

NW lets cm 2 body A.Its at rest and in contct wd body B. BY PROPRTY OF INERTIA IT WNTS TO REMN IN ITS OWN POSTN OF REST. bt friction opposes reltv motion betwn bodies in contact so frctn acting on body A cz of body B wl b fwd to kp thm in contkt n avd reltv motn.

kp in mnd frctn never opposes motn it opposes relatv motion betwn bodies in contct so itrs direction is takin accordng to ths.

tc

According to the defination friction, friction opposes the relative motion btw the 2 bodies in contact.

From eg, body B moves in the fwd direction. Here, relative motion btw ground & lower surface of B occurs.

So, boby B moves fwd & ground is at rest. BY def, friction of body B is in backword direction, to stop relative motion.

Now for body A, it is at rest & contact with B. By inertia,  IT WNTS TO REMN IN ITS OWN POSTN OF REST. bt friction opposes reltv motion betwn bodies in contact so frctn acting on body A cz of body B wl b fwd to kp thm in contkt n avd reltv motn.