# Finding the change in length of a nylon string

## Homework Statement

A nylon tennis string on a racket is under a tension of 225 N. If its diameter is 0.97 mm, by how much is it lengthened from its untensioned length of 29.6 cm?

Li= 29.6cm =.296 m
r= 4.85e-4 m
A= 7.389811319e-7
F= 225 N
E= Young's Modulus for Nylon= 5 x 10^9
Solving for deltaL

## Homework Equations

A=pi(r)^2
F= E (delta L/Li) A

## The Attempt at a Solution

I've found the area and tried using the equation above but did not get a correct answer. I may well have messed up the calculations because that equation confuses me a little and I seem to be algebraically challenged this fine morning.
All my incorrect answers so far are:
14.5e-8 cm
7.470483757e-8 cm
14.506204362e-7 cm
7.470483757e-6 cm (the last three answers came from the equation above)

Any help is greatly appreciated! Thank you!

Related Introductory Physics Homework Help News on Phys.org
rock.freak667
Homework Helper
$$\Delta L = \frac{FL}{AE}$$

what units are E in?

$$\Delta L = \frac{FL}{AE}$$

what units are E in?
I've been trying to find the equation in latex... :/ E is in N/m^2.

rock.freak667
Homework Helper
I've been trying to find the equation in latex... :/ E is in N/m^2.
I was just checking to see what units the value of E you quoted were in.

But try plugging the number back in and checking again, you aren't supposed to get such small changes in length.

I was just checking to see what units the value of E you quoted were in.

But try plugging the number back in and checking again, you aren't supposed to get such small changes in length.
Okay I plugged everything into it and got an answer but I need to be sure it's right. I only have one more try. :/ Would the answer be 1.802481745?

PS: I love your signature. Makes everything so much simpler. : )

rock.freak667
Homework Helper
Okay I plugged everything into it and got an answer but I need to be sure it's right. I only have one more try. :/ Would the answer be 1.802481745?
If you mean 1.8025 cm, then I believe so as that looks better than 14.506204362x10-7 cm

If you mean 1.8025 cm, then I believe so as that looks better than 14.506204362x10-7 cm
Where did that answer come from? And sorry about the long numbers. My homework website is extremely picky

rock.freak667
Homework Helper
Where did that answer come from? And sorry about the long numbers. My homework website is extremely picky
1.802481745 what unit is this in?

for the other number, I just quoted one of your above answers.

1.802481745 what unit is this in?

for the other number, I just quoted one of your above answers.
Centimeters. The final answer is supposed to be in centimeters so I multiplied the answer from the equation by 100.

Oh yeah I forgot about that one. :/ That was early this morning.

rock.freak667
Homework Helper
Centimeters. The final answer is supposed to be in centimeters so I multiplied the answer from the equation by 100.

Oh yeah I forgot about that one. :/ That was early this morning.
then 1.802481745cm should be it.

then 1.802481745cm should be it.
That it is! Thank you very much for your help, sir.