Finding the center of mass of a piecewise function

In summary, finding the center of mass of a piecewise function involves calculating the average position of the mass distribution across different segments of the function. This process typically requires determining the area of each piece, using integrals to find the centroid for each segment, and then combining these results to obtain the overall center of mass. The final calculations take into account the varying densities and lengths of each piece, ensuring an accurate representation of the entire function's mass distribution.
  • #1
JorkThePork
3
0
Homework Statement
Find the center of mass of the "lightning bolt" shaped piecewise function as shown below (or in the desmos project: https://www.desmos.com/calculator/g6crwsecp1)
Relevant Equations
Xcm = A^-1 * ∫ a b x * (f(x) - g(x)) d x

Ycm = A^-1 * ∫ a b .5((f(x)^2 - g(x)^2) d x
desmos-graph.png
I understand that I can divide this shape into a few parallelograms and a triangle and calculate the center of mass of each, but am confused as to what I should do after that. My physics teacher also wants us to use integrals, but I'm assuming I can calculate the COM of each parallelogram and triangle by simply integrating.
 
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  • #2
You can find the CM of the two parallelograms and the half-parallelogram which will give you 3 point masses at the locations of these CMs. Then you can find the CM of the 3 point masses the usual way.
 
  • #3
kuruman said:
You can find the CM of the two parallelograms and the half-parallelogram which will give you 3 point masses at the locations of these CMs. Then you can find the CM of the 3 point masses the usual way.
the two seemingly big parallelograms actually are not parallelograms because of how I designed the lightning bolt (the equations I used are here https://www.desmos.com/calculator/g6crwsecp1). However, I could break the shape up into 2 big parallelograms, 2 very thin parallelograms, and a triangle. I'm assuming I could still then find the CM of the 5 point masses the usual way.
 
  • #4
JorkThePork said:
the two seemingly big parallelograms actually are not parallelograms because of how I designed the lightning bolt (the equations I used are here https://www.desmos.com/calculator/g6crwsecp1). However, I could break the shape up into 2 big parallelograms, 2 very thin parallelograms, and a triangle. I'm assuming I could still then find the CM of the 5 point masses the usual way.
Yes, you can carve it up into simple non overlapping shapes, but since you have equations why not just integrate them and add the (signed) results?
 
  • #5
haruspex said:
Yes, you can carve it up into simple non overlapping shapes, but since you have equations why not just integrate them and add the (signed) results?
Sorry, I’m a little confused how this would give me the center of mass. wouldn’t this just give the area?
 
  • #6
JorkThePork said:
Sorry, I’m a little confused how this would give me the center of mass. wouldn’t this just give the area?
So what do you need to multiply the expressions by before integrating?
 
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FAQ: Finding the center of mass of a piecewise function

What is the center of mass of a piecewise function?

The center of mass of a piecewise function is the point at which the function's mass distribution is balanced. It is essentially the weighted average position of the mass, taking into account the different segments of the piecewise function.

How do you find the center of mass for a piecewise function?

To find the center of mass of a piecewise function, you need to integrate the function over its entire domain, taking into account the different segments. You calculate the moment of the function about a point (usually the origin) and then divide by the total mass. Mathematically, this involves computing the integral of x*f(x) over the domain and dividing it by the integral of f(x) over the same domain.

What are the steps involved in calculating the center of mass for a piecewise function?

The steps to calculate the center of mass for a piecewise function are: 1. Divide the function into its segments.2. Compute the integral of x*f(x) for each segment.3. Compute the integral of f(x) for each segment.4. Sum the integrals from steps 2 and 3 over all segments.5. Divide the total moment (from step 2) by the total mass (from step 3) to find the center of mass.

What are common challenges when finding the center of mass of a piecewise function?

Common challenges include correctly setting up the integrals for each segment, ensuring continuity at the boundaries of the segments, and accurately performing the integration, especially if the function is complex or involves discontinuities. Additionally, errors can arise if the limits of integration are not properly managed.

Can software tools help in finding the center of mass of a piecewise function?

Yes, software tools like MATLAB, Mathematica, and Python (with libraries like NumPy and SciPy) can significantly simplify the process of finding the center of mass of a piecewise function. These tools can handle complex integrations and provide accurate results quickly, reducing the risk of manual calculation errors.

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