Q.

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 the upper wire to that of the lower wire will be _____.

[Area of cross-section of wire = 0.005 cm2, Y = 2×1011 Nm-2 and g = 10 ms-2]   [2024]


Ans.

(3)

fnet=0

T2=T1+2g=g+2g=3g

T1=g                 ...(i)

(stress)L=Y×(strain)L

(strain)L=stressY=FYA

(strain)upper=T2YA

(strain)lower=T1YA

(strain)upper(strain)lower=T2T1=3gg=3