# Minimizing Friction : Science

### Minimizing Friction : Science CBSE / NCERT Revision Notes

Friction is a necessary evil. Without friction, we cannot walk, hold articles, the brakes of automobiles do not work, and the power of a motor cannot be transferred to a grinding machine.

• Friction is not only a helpful but also a hindrance at times.
• Wearing out of footwear is a very common example of friction.
• Sound from the fans and creaking of the door are also result of friction.

### Minimizing Friction:

However, friction is undesirable in certain areas and we need to reduce it. Removing friction completely is not possible. But, it can be minimised.
• Friction between the sliding surfaces of two objects can be reduced by making the surfaces in contact smooth by polishing the surfaces.
• Sliding friction between the moving parts of vehicles can be reduced by using oil, grease or graphite.
• In electrical plugs, graphite is used to reduce friction between the plug pins and the corresponding socket.
• In certain machines, like the drill used by a dentist, a layer of air is used as a lubricant to reduce friction between the moving parts.

In the manufacturing industry, machinery parts tend to wear out because of friction. Some machines may even start consuming more fuel because of this reason.

The interlocking of irregularities on the surfaces of two bodies in contact, which cause friction, is overcome to great extent by the use of lubricants, the material used to reduce friction.

Rolling friction is less than sliding friction. Hence, sliding friction is replaced by rolling friction by using rollers, like ball bearings between the hub and the axles in the moving parts of machines and vehicles.

When an object moves through a fluid, the friction offered is called fluid friction. It is also called drag. Fluid friction depends on the shape of the object and the nature of the fluid. Aero planes, boats, fishes and birds which move through fluids have bodies of special shape so as to reduce the friction due to fluid and avoid energy loss. The special shape of Aero planes, boats, fishes and birds which reduces the drag is called streamlined shape.

Aeroplanes and boats are designed to help minimise fluid friction and avoid energy loss.

The factors on which drag depends are:
• The speed of an object with respect to the fluid
• The shape of the object
• The nature of the fluid

The shape of an aircraft that is specially designed to reduce the drag is called an aerodynamic shape.

The magnitude of drag exerted by each fluid is different.