Friction (part-4)

FRICTION

Q.8. Friction is a necessary evil. Justify it through few examples.
Ans. Friction basically results in three kinds of aspects, on the basis of which we say that friction is a necessary evil. These aspects are Gripping, Rubbing and Heating.
Advantages of friction:
  • We would not be able to stand, walk or run if there had not been any friction.
  • Had there been no friction between the tyres of the automobiles and the road, they could not be started or stopped or turned to change the direction of motion.
  • It will not be possible to stop a moving object without friction.
  • Friction helps us to write on a paper.  The force of friction exists between the tip of a pen or pencil and paper. Similarly, when we write with chalk on the blackboard, its rough surface rubs off some chalk particles due to friction which stick to the black board.
  • Friction between belt and pulley helps in rotation of the different parts of machine.
  • Without friction, no building could be constructed.
  • The nails and screws would not be able to hold together in the absence of friction.
  • It would not be possible to light a matchstick by rubbing it against the matchbox if there was no friction.
Disadvantages of friction:
  • It wears out the materials whether they are screws, ball bearings, tyres or soles of shoes. 
  • Some of the force applied to run a machine is wasted in overcoming friction between its moving parts. As a result the efficiency of the machine reduces. Due to friction the energy consumed by the machine for operation increases. 
  • Friction is also responsible for the production of noise in machines.
  • When a machine is operated, heat generated causes much wastage of energy.
Q.9. Write some ways by which friction can be increased.
Ans. Friction is desirable in some situations, so it can be increased by few methods:
  • Sand and gravel are spread over the slippery ground during rainy season to make the road rough, then it becomes easier to walk on ground.
  • Shoes are made with grooves and spikes to provide the shoes better grip on the floor, so that we can move safely.
  • Handles of vehicles have rubber grips with spikes in it for a better grip.
  • The treaded tyres of cars, trucks and bulldozers provide better grip with the ground.
  • We deliberately increase friction by using brake pads in the brake system of bicycles and automobiles.
  • kabaddi players rub their hands with soil for a better grip of their opponents.
  • Gymnasts apply some coarse substance on their hands to increase friction for better grip.
  • Parachutes are designed to increase air friction for safe landing.
Q.10. Write some ways by which friction can be decreased.
Ans. Friction is undesirable in some situations, so it can be decreased by few methods:
  • By using lubricants. Lubricants are the substances which fill the grooves present between the two surfaces. As a result,  surfaces of the objects can glide easily over one another as a smooth layer is created between two solids. Hence, friction is reduced considerably on using lubricants. For example: oil, grease or graphite etc.
                                           
  • Wheels under objects reduce friction.
  • Ball bearings between two moving objects reduce friction.
  • Sprinkle fine boric based powder on the carrom board to facilitate smooth surface of carom board while playing.
  • Friction can be decreased by making body streamlined in case of fluids.
  • An air cushion between the moving parts is used to reduce friction. 

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