Though friction opposes relative motion yet in certain cases friction is also the cause of motion In fact without friction , motion cannot be started , stopped or transferred from one body to the other . Read the above passage and answer the following questions
(i) Give one example where friction cause motion
(ii) Give the direction of friction on front wheel and rear wheel of a bicycle when it is pedaled and when pedaling is stopped
(iii) frictions is a necessary evil What does this imply in day to day life ?

Explanation

(i) When a person pushes the ground backwards rough surface of ground reacts and exerts a forward force due to friction which causes motion
(ii) When a bicycle is pedalled the rear wheel moves by the force communicated to it by pedalling while front wheel moves by itself Therefore force of friction on rear wheel is in forward direction and force of friction on front wheel is in the bacward direction However when pedalling is stopped both the wheels move by themselves Therefore force of friction on both the wheels is in the opposote direction
(ii) Friction is a necessary evil because inspite of many disadvantages of frictions we cannot do without friction the same is true in day to day life Mad rush to surge ahead of our peers gives rise to cut throat competiton which is an evil like frictions but is necessary for progress .