Calculating the Tensile Strain of a Glass Rod

[tone999]

Homework Statement

If a glass rod of diameter 1cm is loaded with a 1kN tensile load and has a young's modulus of 70 GPa, what is the tensile strain?

Homework Equations

The Attempt at a Solution

Im sure if somebody could tell me the formula for this i could work it out easily

 

[alphysicist]

Hi tone999,

Homework Statement

If a glass rod of diameter 1cm is loaded with a 1kN tensile load and has a young's modulus of 70 GPa, what is the tensile strain?

Homework Equations

The Attempt at a Solution

Im sure if somebody could tell me the formula for this i could work it out easily

Young's modulus is an example of a modulus of elasticity. What is the mathematical definition of a modulus of elasticity?

 

[tone999]

elastic modulus = stress/strain

70,000 = 0.01/1000

Answer in pascal units

Is this anywhere near the correct method?

 

[tone999]

Strain = 1kN / ((pi*1^2)/4 * 70GPa) = 1kN / (.7854cm^3 * 70GPa)

Strain = 1000N / (785mm^2 * 70000 N/mm^2) = 0.000182

Is this correct now?

 

[alphysicist]

Strain = 1kN / ((pi*1^2)/4 * 70GPa) = 1kN / (.7854cm^3 * 70GPa)

Strain = 1000N / (785mm^2 * 70000 N/mm^2) = 0.000182

Is this correct now?

Yes, that looks right to me.

 

[tone999]

If that rod, with thermal expansion coefficient 6 x10^-6 is cooled
by 20 OC, what is the resulting thermal strain?

Is this just 6x10^-6/(20)(0.000182)=5.46x10^-11