One end of a metal wire is fixed to a ceiling and a load of 2 kg hangs from the other end. A similar wire is attached to the bottom of the load and another load of 1 kg hangs from this lower wire. Then the ratio of longitudinal strain of upper wire to that of the lower wire will be ____. [Area of cross section of wire =0.005cm2, Y=2×1011Nm−2 and g=10ms−2]
Answer: 3
Solution
The upper wire carries the weight of both loads, F1=(2+1)g=30 N, while the lower wire carries only the 1 kg load, F2=1×g=10 N. Longitudinal strain is ϵ=AYF; since both wires have the same A and Y, the ratio of strains equals the ratio of tensions: ϵ2ϵ1=F2F1=1030=3.
JEE Main · 2024 · 01 Feb 2024 · Shift 2 · Integer answer