2013 GS Paper I, all questions
UPSC Prelims 2013 · GS Paper I
Question 88: Science and Technology
Ball bearings are used in bicycles, cars, etc., because
athe actual area of contact between the wheel and axle is increased
bthe effective area of contact between the wheel and axle is increased
cthe effective area of contact between the wheel and axle is reduced
dNone of the above statements is correct
AnswerUPSC’s answer is (c).
Ball bearings replace sliding friction between the wheel and the axle with rolling friction, because the balls roll between the two surfaces. Only a small part of each ball touches the surfaces at any moment, so the effective area of contact is reduced, which reduces friction and wear. Rolling friction is much smaller than sliding friction.
Why each option is right or wrong
- (a) Wrong. The contact area is reduced, not increased.
- (b) Wrong. The effective area of contact is reduced, not increased.
- (c) Correct. The effective area of contact is reduced and friction falls.
- (d) Wrong. Statement (c) is correct.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2013, General Studies Paper I, Series A. The paper on upsc.gov.in.