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# Young's moduli of elasticity help!

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Produce a value for Young's moduli of elasticity using the following conditions:

A rod diameter between 5mm-10mm

An extension of between 0.00115 and 0.00355

A rod length between 55mm and 90mm

A force of 15kN is applied on the rod.

Really struggling to get my head around Young's mod

Oct 1, 2019

#1
+29249
+3

Young’s modulus is stress divided by strain.

Stress is force per unit (cross-sectional) area.

You are given the force.

Choose a diameter from the range given (at least, I assume that’s what you are meant to do as you give no other information). From the diameter, d, calculate the area, A = pi*d2/4.

Hence calculate the stress.

Strain is extension divided by original length.

Choose an extension from the given range (which is presumably in mm).

Choose an original length from the range given.

From these get the strain.

Divide the stress by the strain to get Young’s modulus.

Note that the result will have units of whatever units you choose for force divided by the square of the units you choose for the diameter (strain is dimensionless).

Oct 1, 2019

#1
+29249
+3

Young’s modulus is stress divided by strain.

Stress is force per unit (cross-sectional) area.

You are given the force.

Choose a diameter from the range given (at least, I assume that’s what you are meant to do as you give no other information). From the diameter, d, calculate the area, A = pi*d2/4.

Hence calculate the stress.

Strain is extension divided by original length.

Choose an extension from the given range (which is presumably in mm).

Choose an original length from the range given.

From these get the strain.

Divide the stress by the strain to get Young’s modulus.

Note that the result will have units of whatever units you choose for force divided by the square of the units you choose for the diameter (strain is dimensionless).

Alan Oct 1, 2019