Question

explain with 2 examples - where it is to increase magnitude of friction

Answer 1

Introduction to the ways of increasing and decreasing friction:

When a body slides over the surface of another body, there is an opposing force acting in opposite direction of motion and this opposing force is called friction.Their are various ways by means of which, we can increase or decrease friction. At times it becomes necessary to increase or to decrease friction. As in case of a weightlifter lifting weights, he/she applies some powder to have a hold or grip that increases the friction. In machinery parts it becomes a necessity to reduce or decrease friction by applying lubricants, so as to minimize the effects of heat released that might harm it, Let us discuss more on it.

Method of decreasing and increasing friction

Method of decreasing friction:

By polishing: Friction between two surfaces can be reduced by polishing them. The interlocking and projections are minimized by this method.Ball-bearing:  As the rolling friction less than the sliding friction consequently in rotating machinery, the shafts are fixed on the ball bearing so that the friction can be reduced considerably. For example-the free wheel of a cycle, the axle of a motorcar, the shafts of the motor dynmo etc. are provided with ball-bearing.Lubricants: Friction between two surfaces can be decreased by using lubricants. A lubricant is a substance (a solid or a liquid) which forms a thin layer between the two surfaces in contact. It also fills the depressions present in the surfaces of contact and reduces friction considerably. In light machinery thin oils with low viscosity are used, in heavy and fast moving machinery thick oils and solutes (grease) are used.Streamline: The friction due to air is reduced by making the automobiles streamline.

Methods of increasing friction:

By making the surface rough friction can be increased. Examples of increasing friction-the tyres of a motor car and bicycles are made rough to increase the friction .when a ground or surface become slippery after rain or water splashing it is made rough by spreading sand to increase the friction.