Brass Compression: Solving For ΔL

[kboykb]

Homework Statement

A 1.8- m long brass bar has a square cross section 1.3 cm on an edge. The bar is compressed by a force of 9.0×10^3 N applied to its ends. By how much does the bar shorten (in m)?

Homework Equations

There is an example in our book explaining how to use a variation of Young's Modulus. ΔL = FL/YA

The Attempt at a Solution

Change 1.3 cm into .013 m.

(9.0x10^3 N)(1.8m) / (91 x 10^9 N/m^2)(.013^2) = .0011 m

I squared .013 since it's the area squared.. and the 91 x 10^9 is the value for brass in the Elastic Moduli.

Of course this is wrong, but not sure what I'm not doing quite right.

 

[kboykb]

Nevermind guys, that turned out to be the CORRECT answer.

The online Homework program had the answer listed as .00105 m

Since I was putting .0011 in it did not accept my answer. Go figure *sigh*