Question

A structural steel rod has a radius of 10mm and a length of 1m. A 100k N force streaches it along its length. Calculate:
(a) the stress
(b) elongation
(c) percentage.
Given that the young's modulus of elasticity of the structural steel is 2.0*10(power)11 Nm(power)-2.

chapter- SOLIDS

Answer 1

stress=force per unit CSA
=1000000000/3•14
=3.33×1000000

elongation=stress×original lenght/Young's mod
=3.33×1000000×1/2×10(power)11
=3.33×10(power)-5

percentage=elongation/total length×100
=3.33×10(power)-3/1%

Answer 2

stress=force /csa
=100kN/pi.r^2=100kN/(22/7 (0.01)^2
=(100x7x10000)/22kN/m^2

Young modulus=stress/strain
strain=stress/Young modulus
dl/l=(7x10^9/22)/2x10^11
=(7/44)x10^-2m
dl=(7/44)x10^-2m
where dl is elongation

percentage=(dl/l)x100
=70/44 %