Where is the Center of Mass for a Semicircular Wire?

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SUMMARY

The center of mass for a uniform thin wire bent into a semicircle of radius r is determined using integration techniques. The correct formula for the y-coordinate of the center of mass is given by \(\bar y = \frac {\int_{-R}^{R} y \, dx}{\int_{-R}^{R} \, dx}\), where y is defined as \(\sqrt{r^2 - x^2}\). This approach emphasizes dividing by the diameter of the circle rather than half the area, ensuring accurate calculations. The discussion highlights the importance of proper integration limits and the relationship between units and the physical dimensions involved.

PREREQUISITES
  • Understanding of calculus, specifically integration techniques
  • Familiarity with the concept of center of mass
  • Knowledge of coordinate systems in physics
  • Basic geometry of circles and semicircles
NEXT STEPS
  • Study integration techniques for finding centers of mass in various shapes
  • Explore applications of center of mass in physics problems
  • Learn about the properties of uniform distributions in physical systems
  • Investigate the implications of coordinate transformations in mass distribution
USEFUL FOR

Students and educators in physics, engineers working with structural designs, and anyone interested in the mathematical principles of mass distribution in physical objects.

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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.)
 
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What have you done so far?
 
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...
 
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!
 

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