# Hmwk Help Arc length

• Mar 29th 2009, 09:19 PM
Freemymind
Hmwk Help Arc length
Find the length of the curve.
8. 3x^(3/2) from x=0 to x= 5/9

9. y = 1/6 x^3 + 1/(2x) from x=1, to x=5
17) The spring of a spring balance is 6.0 in. long when there is no weight on the balance, and it is 9.0 in. long with 8.0 lb hung from the balance. How much work is done in stretching it from 6.0 in. to a length of 14.5 in.?
• Mar 29th 2009, 09:44 PM
n0083
Please show your attempts, or any equations/formulae presented to you.
Namely, please provide the general arc length equation.
• Mar 29th 2009, 10:23 PM
Freemymind
http://http://prepcalcabc0607.blogsp...rc-length.html

I cant seem to post the formula buts its in this website for arc length. thank you in advance.
• Mar 29th 2009, 10:47 PM
n0083
Quote:

Originally Posted by Freemymind
Find the length of the curve.
8. 3x^(3/2) from x=0 to x= 5/9

the link you provided is broken.

one form of the arc length is:

$\int_{a}^{b} \sqrt{1+(f'(x))^2} \, dx$

What do you get for $f'(x)$? a? and b?
• Mar 29th 2009, 11:12 PM
Freemymind
does a=0 and b= 5/9 I got the anti derivative of the function which is
(6/5) x^(5/2)
• Mar 30th 2009, 12:02 AM
JeremyH
You need to take the first derivative before you calculate the integral. Look at the equation n0083 posted, but yes your a and b are correct.