Question

Kinetic friction acts opposite to relative acceleration

Answer 1

the direction of the friction forces is opposite to the
pending relative motion of the surface.
if the force (p) increase . until F Fs (limiting static frictional force ) if F= Fs, then the block is unstable equilibrium and block will move . .... also draw on normal forces.

Answer 2

hi mate

Kinetic friction is a result of two surfaces sliding with respect to each other. That friction tends to resist the relative motion. Most of the time, that means that the frictional force on some object is in the opposite direction of its motion - that is, it tends to slow it down. Think of a block sliding on a horizontal surface, the frictional force opposes the motion. (But there is a case where the kinetic friction can be in the direction of the motion - and, in fact, can cause an acceleration in that direction. But I’ll get to that in a bit.)