Basics of Friction

Physics of Frictional force

Friction is a force. One that if often covered during our Physics Tuition classes. Friction force can be grouped into several categories according to the scenarios, and they include:

i. Dry friction

This is the frictional force that resists relative lateral motion between two solid surfaces in that are in contact. Dry friction is split into two categories namely static friction and kinetic friction. Static friction is between non-moving surfaces while kinetic friction is experienced between moving surfaces.

ii. Fluid friction

This is the frictional force that exists between layers of a viscous fluid that are moving relative to each other. It occurs in fluids. It can also be termed as drag force.

iii. Lubricated friction

This is the frictional force that exists between a lubricant (fluid) and the solid surfaces that the fluid lubricant separates. While a lubricant greatly reduces the frictional force between two surfaces, it does not eliminate it, and the frictional force involved still needs to be considered in various high precision engineering situations.

iv. Skin friction

This is the force resisting the motion of a fluid across the surface of a body. It a component of drag.

v. Internal friction

This is the force which resists motion between the elements that makes up a solid material when it is being deformed.

Increasing and Decreasing Friction

Friction is increased by making the surfaces in contact rough. If you look at the lower part of your shoe you will see that there are some spikes that are added so as to increase the friction between the sole of your shoe and the ground. On the other hand, friction is reduced by using devices like wheels and bearings and also by using lubricants. Most of the lubricants used are in fluid form but there are some that are in solid form like the graphite. The main reason for using graphite as a lubricant is because graphite has a very high melting point and it will not melt and flow away when the friction between the sliding parts causes a lot of heat.

Advantages of friction

i. Friction is a very important element in automobile brakes since they rely on friction in order to slow the automobile.

ii. Friction is also required in providing rail adhesion which is the grip that the wheels of a train have on the rails.

iii. There also have to be enough friction between your vehicle’s tires and the road for your vehicle to be able to move. Failure to having enough friction, the vehicle will slip.

iv. Friction between the matchstick’s head and the match box’s rubbing surface is used to heat and ignite matchsticks.

Disadvantages of friction

i. Friction causes wear and tear

ii. Friction converts some of the kinetic energy of the two sliding surfaces into heat. This heat if uncontrolled can cause breakdown or even start a fire if it gets into contact with a flammable substance.

iii. Sometimes, friction causes a very irritating screeching noise.