Notes On Minimising Friction - CBSE Class 8 Science
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. However, friction is undesirable in certain cases and we need to reduce it. For example, 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. Therefore friction needs to be removed. But removing friction completely is not possible; it can only be minimised. Methods of Minimising Friction The interlocking of irregularities on the surfaces of two bodies in contact, which cause friction, is overcome to a great extent by the use of lubricants like oil, grease, etc. Friction between the sliding surfaces of two objects can be reduced by making the surfaces in contact smooth by polishing them. 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. 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. Friction is reduced by providing wheels, e.g. suitcase, school bags of kids, etc. Aeroplanes, boats, fishes and birds which move through fluids have bodies of special shape, called streamlined shape, so as to reduce the friction due to fluid and avoid energy loss.

#### Summary

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. However, friction is undesirable in certain cases and we need to reduce it. For example, 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. Therefore friction needs to be removed. But removing friction completely is not possible; it can only be minimised. Methods of Minimising Friction The interlocking of irregularities on the surfaces of two bodies in contact, which cause friction, is overcome to a great extent by the use of lubricants like oil, grease, etc. Friction between the sliding surfaces of two objects can be reduced by making the surfaces in contact smooth by polishing them. 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. 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. Friction is reduced by providing wheels, e.g. suitcase, school bags of kids, etc. Aeroplanes, boats, fishes and birds which move through fluids have bodies of special shape, called streamlined shape, so as to reduce the friction due to fluid and avoid energy loss.

#### Activities

 Activity 1 Phet.colorado has created a beautiful simulation to depict that friction produces heat. When the yellow molecules are rubbed onto the green molecules a rise in temperature is observed. This indicates that friction produces heat. Go to Activity Activity 2  Learningcenter.nsta has created a simulation "Ball on a Flat Surface" which is designed to provide a surface with a selectable amount of friction. In this, the friction slider can be adjusted to set a value for friction and compare how far the ball travels in relationship to other values of friction. Go to Activity

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