Solving Raindrop Paths on Ellipsoid with 4x^2+y^2+4z^2=16

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SUMMARY

The discussion focuses on determining the paths of raindrops sliding down an ellipsoid defined by the equation 4x^2 + y^2 + 4z^2 = 16. The key approach involves using vector calculus, specifically the gradient of the surface, to identify the direction of maximum descent for the raindrops. The Euler-Lagrange equation is suggested for minimizing time along the path, although the participants acknowledge that they have not yet covered this topic. The solution requires identifying the gradient at a specific point on the ellipsoid, typically the top, to derive the relationship between x, y, and z.

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  • Understanding of vector calculus concepts, particularly gradients
  • Familiarity with the Euler-Lagrange equation for optimization problems
  • Knowledge of ellipsoidal geometry and its equations
  • Basic integration techniques for calculating paths
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  • Learn how to compute gradients for multivariable functions
  • Explore the geometric properties of ellipsoids and their equations
  • Practice solving integrals related to path optimization in physics
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Mathematicians, physicists, and engineering students interested in vector calculus applications, particularly in optimizing paths on curved surfaces like ellipsoids.

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We have an ellipsoid with the equation 4x^2 + y^2+ 4z^2 = 16, and it is raining. Gravity will make the raindrops slide down the dome as rapidly as possible. I have to describe the curves whose paths the raindrops follow. This is probably more vector calculus than physics, but i wasn't sure how to solve it, so i don't know if knowledge of physics is necessary. I found the gradient, and i know that the rain will probably flow where the gradient is largest; however, i don't know how to go on.
 
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my guess is you need the Euler-Lagrange equation... trying to minimize the time, time=integral(ds/v)...
 
we haven't learned that quite yet, but thanks; I have a strong feeling the gradient of the surface is involved, but I don't see how one can get the curves by taking the path of maximum descent.
 
You can certainly answer this by finding the gradient...however, the drops will follow the path of the NEGATIVE gradient. To me, this should be a sufficient answer. To find a CURVE you would need to know the specific point from which you assume the rain drops originate on the ellipsoid (the top of the ellipsoid?) If the drops originate from the top of the ellipsoid just determine the direction of the gradient by plugging in the point. Then you can determine the line that describes the orientation of the gradient, which is a relationship between x and y. plug in y as a function of x into your original equation and solve for z. The result is z as a function of x, which represents a cross section of the ellipsoid.
 

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