Streching of a String?

Question

A 0.50m long guitar string, of a cross-sectional area 1.0x10^-6 m^2., has a youngs modulas of 2.0x10^-9 n/m^2. how much would you have to stretch the string to get a tension of 20 N?

Answer 1

Stress = E*strain, where E is the Young's modulus. Then

strain = stress/E

tension = stress times area (total force on the string)
total stretch = strain times length

You can now put it all together

stretch = length * tension / (area * E)