Question

Compare and contrast four types of friction

Answer 1

Some of these frictions depend on the Pressure, temperature of atmosphere.

Static Friction: This is the  friction force when two objects in contact  are not moving relative to each other. This friction is higher than kinetic friction.

Kinetic or Dynamic friction: this the friction force opposing the motion of objects, when two objects in contact are in motion relative to each other.  It is less than the static friction. The two surfaces are rubbing against each other as they move.

Rolling friction:  This is the friction when two objects are in contact and one object is rolling over the other - like a wheel on a road. The point of contact appears as stationary. The rolling friction is very less compared to static friction & dynamic friction.

Lubricated friction: this is the friction between two solid surfaces in contact with a layer of lubricant fluid flowing in between them. This friction is the least.

Fluid friction - viscosity :  this is friction between two adjacent layers that are moving relative to each other at different speeds in a fluid.  This is not high.

Internal friction: when an object is compressed and forced to deform, like in a piece of rubber, there is friction between the layers, that opposes this deformation.

Skin friction is the friction that opposes movement of a fluid across a solid surface.  This is also called drag.  When a coin is dropped in water, there is a friction called drag on the coin. Same is the case when a ball is thrown, a drag is experienced by the ball due to the drag of air.