Properties of Matter 1 Question 20

20. In Searle’s experiment, which is used to find Young’s modulus of elasticity, the diameter of experimental wire is D=0.05cm (measured by a scale of least count 0.001cm ) and length is L=110cm (measured by a scale of least count 0.1cm). A weight of 50N causes an extension of l=0.125cm (measured by a micrometer of least count 0.001cm ). Find maximum possible error in the values of Young’s modulus. Screw gauge and meter scale are free from error.

(2004, 2M)

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Answer:

Correct Answer: 20. 1.09×1010 N/m2

Solution:

  1. Young’s modulus of elasticity is given by

Y= Stress  Strain =F/Al/L=FLlA=FLl(πd24)

Substituting the values, we get

Y=50×1.1×4(1.25×103)×π×(5.0×104)2=2.24×1011N/m2

Now, ΔYY=ΔLL+Δll+2Δdd

=(0.1110)+(0.0010.125)+2(0.0010.05)=0.0489

ΔY=(0.0489)Y=(0.0489)×(2.24×1011)N/m2

=1.09×1010N/m2



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