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A small body having mass 1kg is rotating in a circle of radius 10cm. It is connected to the centre with the help of a string having young’s modulus = 1011N/m2. Find change in length of wire while the mass is rotating with constant speed of 2m/s. The cross sectional area of string is 1cm2.

A small body having mass 1kg is rotating in a circle of radius 10cm. It is connected to the centre with the help of a string having young’s modulus = 1011N/m2. Find change in length of wire while the mass is rotating with constant speed of 2m/s. The cross sectional area of string is 1cm2. Correct Answer 0.4μm

Tension ‘T’ in string will be given by T = mv2/R = 1*4/0.1 = 40N. Stress = Y*Strain, where Y is young’s modulus. T/A=Y*ΔL/L ∴ ΔL = TL/AY = (40*0.1)/(0.0001*1011) = 4*10-7m = 0.4μm.

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