Why the coefficient of friction between two surfaces in contact varies directly with the normal reaction ?

Coefficient of friction between two surfaces in contact is always less than_____.

The frictional force between two. surfaces is independent of

A body weighing 10 kg rests on a horizontal surface, the co-efficient of static friction between the surfaces being 0.364. Find the horizontal force needed just to pull the block

A block placed on a horizontal surface is being pushed by a force F making an angle theta with the vertical. The coefficient of friction between the block and surface is mu The force required to slide down the block with uniform velocity on the floor is

A body of mass 2 kg is dragged with a velocity of 2 m/s on a rough horizontal plane. The coefficient of friction between the body and the surface is 0.10. Calculate the amount of heat generated in 5 sec (J=4.2"joule"//calandg=9.8m//s^2)

The ratio between force of limiting friction to the normal reaction gives_____.

The temperature coefficient of most reaction lies between.