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In order to stop a car in shortest distance on a horizontal road, how should one apply brakes? (a) apply the brakes very hard so that wheels stop rotating. (b) apply the brakes hard enough to just prevent slipping (c) pump the brakes( press and release) (d) shut the engine off and not apply brakes. I know the answer is (b). Please give a solution of it so as to why (b) is the answer.


In order to stop a car in shortest distance on a horizontal road, how should one apply brakes? 


(a) apply the brakes very hard so that wheels stop rotating.


(b) apply the brakes hard enough to just prevent slipping


(c) pump the brakes( press and release)


(d) shut the engine off and not apply brakes.


 


I know the answer is (b). Please give a solution of it so as to why (b) is the answer.


 


Grade:

1 Answers

AJIT AskiitiansExpert-IITD
68 Points
10 years ago

Dear student ,

applying equaiton v2 = u2 +2as to the centre of mass of wheels ,  now in every case v and u are same .so to minimize s we need to maximise a . i.e force , retarding force i.e friction. so if we can apply static friction in opposite direction than it will be best possible option . which is (b)  as in rotating motion the velocity of lowermost point is zero and so friciton is static . in (a) friciton will be kinetic which is always leser than static.

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