How much is it lengthened from its untensioned length of 30.2 cm?

[mathcrzy]

Homework Statement

A nylon tennis string on a racket is under a tension of 245 N. If its diameter is 0.92 mm, by how much is it lengthened from its untensioned length of 30.2 cm?

Homework Equations

F=E(delta L/L initial)A

The Attempt at a Solution

245N=(5e9)(?/30.2)(.0266)

delta L = 6.1e-8cm

 

[mgb_phys]

You know the stress, to find the strain you need to know Young's modulus for Nylon.
That is the ratio of the stress to the strain ( can't remember which way round )

 

[mathcrzy]

elastic modulus for nylon is 5e9

 

[aq1q]

that seems right. does that not match with the answer? Its been a while since i used that equation

 

[hotcommodity]

So you'll want to convert the diameter and the "untensioned length" to meters. Also, you want to think of the cross sectional area as the area of a circle, which you know the diameter of. Does that help?

 

[aq1q]

oh you it has to be in meters. and mm is 1x 10^-3 meters.