Friction is the force that resists the relative motion of solid surfaces, fluid layers and elements that slide against each other. Friction is of several types fluid friction, lubricated friction, internal friction, skin friction, dry friction and sliding friction.
Dry fiction is the relative resistance in the lateral motion of two solid surfaces which are in contact.
Fluid friction is described as the friction between the layers of viscous fluid.
Lubricated friction is the fluid friction where a lubricating fluid separates two solid surfaces.
Internal friction is the force that resists the motion between the elements that make up a solid material while it undergoes distortion.
Skin friction is the force the resists the motion of a fluid across a body surface.
Disadvantages of Friction:
Friction produces heat in various parts of machines, this one of the main disadvantage of friction. In this way some of the useful energy is wasted as heat energy.
More power has to be exerted on machines due to friction.
Friction opposes motion.
Noise is also produced in machines due to friction.
Engines of automobiles consume more fuel due to friction.
Efficiency of machine is decreased; energy is lost due to heat.
Friction counteracts movements and so it takes more energy to move. It causes unwanted heat.
Rubber shoes or soles are worn out due to friction.
Friction between trees causes forest fires.
Friction slows down or stops the movement of objects. For example: A bicycle will stop eventually if it is not cycled consistently and continuously. If the bicycle has to be sped up, it has to be cycled faster. Hence, it more energy is needed to overcome the frictional force.
Friction causes the surface of an object to wear out. For example: Soles of shoes and surface of tyres are worn out due to friction.
Friction produces unnecessary heat. For example: Engines of cars becomes hotter due to friction.