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UPSC Civil Service Exam Questions - Engineering

Q1:

A mild steel bar is in three parts, each 20 cm long. The diameters of parts AB, BC and CD are 2 cm, 1 cm and 3 cm respectively. The bar is subjected to an axial pull of 4t as shown in the given figure. If E = 2 x 106 kg/cm2 and the elongations in the three parts of the bar are Δ1, Δ2 and Δ3 respectively, then the ratio of the greatest to the least of these elongations will be

A 9

B 4

C 3

D 2

ANS:C - 3

Elongation is inversely proportional to area.


@All
Here, Most of us will solve this question considering the bars as rectangular and will come out with an answer = 3, which is wrong.

You have to consider these bars as circular and you will get an answer =9, which is correct.