Gradient and Divergence in spherical coordinates

  • Thread starter Thread starter physicss
  • Start date Start date
  • Tags Tags
    Spherical
AI Thread Summary
The discussion centers on the divergence of a vector field expressed in spherical coordinates, specifically the components involving er, e(θ), and e(φ). There is a disagreement regarding the expression for the vector field, with one participant presenting a different form for e(θ) and raising questions about the dimensional consistency of the scalar field. The conversation highlights the importance of using LaTeX for clarity in mathematical expressions. It is emphasized that the gradient can be derived in spherical coordinates through direct substitution and basic linear algebra, which also allows for the computation of divergence, curl, and the Laplacian. Overall, the thread focuses on the mathematical formulation and consistency of vector fields in spherical coordinates.
physicss
Messages
25
Reaction score
4
Homework Statement
Hello, are my answers correct?

I had to calculate the gradient of f=z and f=xy in spherical coordinates.
My solution for f= z is: cos(θ) er+ (-sin(θ)) e(θ)

f=xy

rsin^2(θ)sin(2φ) er+ rcos(θ)cos(φ)sin(θ)sin(φ) e(θ)+ rcos(2φ)sin(θ) e(φ)

I also had to calculate the divergence of the following vectorfield (Image)

My result is: (scalarfield)

Sin^2(θ)cos^2(φ) er + rcos(2θ)cos^2(φ) e(θ)-rsin(θ)cos(2φ) e(φ)


Thanks in advance
Relevant Equations
er, e(θ) and e(φ) are the spherical base vectors
9527BE5E-8449-4D24-8FA2-A3BE2FC41DD0.jpeg

Vectorfield for the divergence
 
Physics news on Phys.org
physicss said:
rsin^2(θ)sin(2φ) er+ rcos(θ)cos(φ)sin(θ)sin(φ) e(θ)+ rcos(2φ)sin(θ) e(φ)
I get a slightly different ##\vec e_\theta##.
Please learn to use LaTeX.
 
physicss said:
My result is: (scalarfield)

Sin^2(θ)cos^2(φ) er + rcos(2θ)cos^2(φ) e(θ)-rsin(θ)cos(2φ) e(φ)
If it is a scalar, how come it has ##\vec e_r## etc?
I also note a dimensional inconsistency.
 
You can get the gradient in spherical (or any other) coordinates by direct substitution, using basic linear algebra. From there you can get div, curl, and the Laplacian just by vector operations:
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top