# Homework Help: Total mass of a cord, uniform density

1. Aug 31, 2011

### RedAnsar

1. The problem statement, all variables and given/known data
http://i54.tinypic.com/2uztu6d.jpg

2. Relevant equations
I don't know how to use LaTeX, sorry...

mass = L times integral of density, where the endpoints are the bounds of the region.
However, in this case...it seems to me that things are reserved...

3. The attempt at a solution

I just really don't understand. I thought perhaps I should try and integrate the position function, but...well, that's sort of trivial, and I'm supposed to get an integral in the form of the hint, so that's definitely not the right way to think about it...the density is constant, so I guess I need to break up the cord into little pieces, and integrate that, I guess using parametrization? A line integral??

Sorry for the ridiculous question,
RedAnsar

2. Aug 31, 2011

### rock.freak667

Wouldn't you need to get the arc length from -5 to 5 and then multiply that by the density?

3. Aug 31, 2011

### stallionx

The density here is defined as kg/m

so it would make sense that you find the cord length and multiply by density to obtain mass.

Hint : dS**2=dx**2 + dy**2