# Homework Help: Center of mass for a thin wire

1. Oct 17, 2004

### physicsss

A uniform thin wire is bent into a semicircle of radius r. Determine the coordinates of its center of mass with respect to an origin of coordinates at the center of the "full" circle. (The semicircle is in the positive y plane.)

2. Oct 17, 2004

### Tide

What have you done so far?

3. Oct 17, 2004

### physicsss

I've tried to integrate sqrt(r^2-x^2) from -r to r, and then divide it by half the area of the circle...

4. Oct 17, 2004

### Tide

That's a good start! Instead of dividing by half the area of the circle divide by the diameter of the circle instead:

$$\bar y = \frac {\int_{-R}^{R} y dx}{\int_{-R}^{R} dx}$$

Your units would provide a clue!