Question

- a- Write the laws of limiting friction
b- define angle of friction
c- define angle of repose
d- what is the relationship between angle of repose and angle of friction

Answer 1

Here we have to deal with the concepts of friction and its associated terminologies.
We know that friction is a force and it always opposes the relative motion between the two objects.
Its SI unit is Newtons, N.

Complete answer:
a- limiting friction is defined as that type of friction which comes into play when the body is at rest. To find limiting friction, we need to have the product of the normal force and the coefficient of limiting friction. The laws of limiting friction are:
(1) The direction of limiting friction force is always opposite the direction of motion.
(2) It always acts tangential to the two surfaces.
(3) It is dependent on the material and the nature of the surfaces in contact.
(4) It is independent of the shape and area.
b- it is defined as the angle that the normal force made with the contact force when the value of static friction is maximum.
c- angle of repose is the angle that angle of an inclined plane, at which a body placed on it just begins to slide.
d- Angle of friction is equal to the angle of repose.

Note:
Friction is sometimes of great use like it helps in walking and in application of brakes, but at other times it is evil as a lot of wear and tear takes place due to it.
The weight of the body always acts vertically downwards.