NEET | 2018Basic Maths and Units and DimensionsHard

Question

Two wires are made of the same material and have the same volume. The first wire has cross-sectional area A and the second wire has cross-sectional area 3A. If the length of the first wire is increased by ∆l on applying a force F, how much force is needed to stretch the second wire by the same amount ?

Options

A.

9F

B.

6F

C.

4F

D.

F

Solution

Y = FlA∆l
∵ V= Al  so l=VA
F=YA∆ll=YA2∆lV
F1F2=A1A2⇒FF2=A3A2=19
F2 = 9F

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