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Mechanical Properties Of Fluids

Question
CBSEENPH11018113

A 4m long wire of radius 4 mm is elongated by 0.01% when loaded by a force of 80π newton. What is the stress in the wire and Young's modulus of wire?

Solution

Length of the wire, l = 4m
Radius of the wire, r = 4 mm = 0.004 m
Force on the wire, F = 80π N 
Strain = 0.01% = 0.0001

Now, using the formula of stress,

Stress = Fπr2  = 80ππ(0.004)2 = 5× 106 N/m2

Young's modulus of the wire is given by, 
Y = StressStrain=5×1060.0001 = 5×1010 N/m2