Unit Normal Vector to a Cylinder

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SUMMARY

The unit normal vector to the cylinder defined by the equation x² + z² = 16 can be determined by calculating the gradient of the function F(x, y, z) = x² + z² - 16. The gradient, given by ∇F = (2x, 0, 2z), provides the direction of the normal vector. To obtain the unit normal vector, one must normalize this gradient by dividing it by its magnitude. Parametrization of the cylinder can also be employed as an alternative method to derive the normal vector.

PREREQUISITES
  • Understanding of gradient vectors in multivariable calculus
  • Familiarity with the concept of unit vectors
  • Knowledge of parametrization techniques for surfaces
  • Ability to compute vector magnitudes
NEXT STEPS
  • Study the process of calculating gradients for level surfaces
  • Learn how to parametrize cylindrical surfaces effectively
  • Explore normalization of vectors in three-dimensional space
  • Investigate applications of unit normal vectors in physics and engineering
USEFUL FOR

Students studying multivariable calculus, mathematicians interested in vector calculus, and engineers working with surface normals in three-dimensional modeling.

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Homework Statement


I need to find the unit normal vector to x2+z2=16. I can find the unit normal vector to every shape but a cylinder, and I can't seem to see how to do it.


Homework Equations


\nablaF=Fxi+Fyj+Fzk


The Attempt at a Solution


I know that I need to find the gradient of the surface equation. I've considered that this gradient may be i-2x-2z. Or am I completely wrong?

If you need more information please say what. Thank you!
 
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You aren't really using your own "Relevant Equation". The level surface equation for your cylinder is F(x,y,z)=x^2+z^2-16=0. Now what is grad(F) again?
 
So if the equation of the cylinder is x^2+z^2=16, i would f(x,y,z)=x^2+z^2, and find the gradient from there.

Then you also have the constraint that it has to be on the cylinder x^2+z^2=16. So I would parametrize that surface, and then plug that parametrization into the gradient to get the equation for the vectors. Then you need to divide by the norm in order to get unit vectors, (which i think might end up very nicely!).

Alternatively, the way i would do it, is just parametrize the cylinder off the bat, then take the derivative, then normalize it (but one doesn't use gradients directly).
 
Wow, that was a terrible oversight on my part. I believe I took that from the other question I was looking at at the time. This gradient would be 2xi+2zk, no?
 
yeep! looks like it!
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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