Question

A uniform wire of steel of length 2.5m and density 8.0g/cm³ weighs 50g. When stretched by a force of 10kgf the length increases by 2mm. Calculate Young's modulus of steel.

Answer 1

We know that young's modulus = stress /strain

volume of the wire = weight/density

=> Area x length = weight / density

=> area = weight/(density * length)

weight = 50 gm = 0.05 kg

density = 8 g/cm³ = 8000 kg/m³

length = 2.5 m

Hence

Area = 0.05/(8000*2.5)

= 2.5 x 10⁻⁶

Stress = force/area

= 10/2.5 x 10⁻⁶

= 4 x 10⁶

Strain = change in length/ original length

=  2 x 10⁻³ m /2.5 m

= 8 x 10⁻⁴

Hence young's modulus = stress / strain

= 4 x 10⁶/ 8 x 10⁻⁴

= 5 x 10⁹

Answer 2

Answer:

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