All Questions
276
questions
2
votes
1
answer
104
views
Calculating deflection on a beam
This is for a hobby project, and to learn a little about elasticity along the way.
I have a triangle wedge comb piece of decreasing width and angle for which the cross section is shown here:
For each ...
- 43.8k
3
votes
1
answer
1k
views
maximal principle uniform covering of a sphere with uniform geodesics
Summary
This question is about covering a sphere with great circles so that the resulting density is uniform and that if we for each circle associate a normal vector, then the magnitude of the sum of ...
CommunityBot
- 1
1
vote
0
answers
96
views
Covariant derivative of a Riemann tensor
I'm trying to calculate the covariant derivative of a Riemann tensor, and I'm using the following way, but there is some problem in my calculations because my calculations do not match with the ...
- 11
0
votes
0
answers
29
views
Algebraic varieties associated with (simple) "string" constructions
It is relatively well-known that any arrangement of points that can be constructed with a straightedge and compass can also be constructed with an unstretchable string (of arbitrary length, negligible ...
- 131
4
votes
1
answer
70
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Modeling Nanotubes Geometry
In various references, we see the construction of unit cells of carbon nanotubes (CNTs) from chiral and translational vectors.
The chiral vector is given as:
$$\vec C_h = n\vec a_1 + m\vec a_2$$
...
- 3,789
3
votes
3
answers
16k
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How to calculate solid angle of a rectangular detector of 20cm x 10cm?
I have an detector of $20\mathrm{cm}\times 10\mathrm{cm}$, how can I calculate the solid angle subtended by the detector if the detector is placed at $30\ \mathrm{cm}$ apart? Because directly I can ...
- 83
1
vote
1
answer
17k
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how to calculate the angle in the $x-y, y-z, x-z$ plane given only $3D$ vector direction and magnitude?
Please help me solve this. I have been thinking of all sorts of ways to solve this but can't figure out how :(. OK here's the problem: I am given a three dimensional velocity vector (I know the ...
- 2,743
1
vote
0
answers
48
views
Clarification Regarding Solid Angle
I am studying Zangwill's Modern Electrodynamics but I'm having trouble following an argument he makes about solid angles in preparation for deriving the integral form of Gauss's law.
He defines the ...
- 319
17
votes
5
answers
10k
views
The vertices of an equilateral triangle are shrinking towards each other
For an equilateral triangle ABC of side $a$ vertex A is always moving in the direction of vertex B, which is always moving the direction of vertex C, which is always moving in the direction of vertex ...
- 10.5k
0
votes
0
answers
33
views
Rearranging trigonometric equation for low speed vehicle turning geometry
I have a set of equations that describe the geometry of a vehicle in low speed turning (a single track vehicle with the assumption that the tyres go in the direction they are pointing). A constraint ...
- 10.5k
0
votes
1
answer
36
views
Precisely defining the overlap depth, or deepest point of overlap, for ellipsoids and spheroids
I was wondering if there is a robust mathematical definition for the 'deepest point of overlap' of ellipsoid (or, equally as good, spheroid) 1 that has overlapped with ellipsoid 2. For non-overlapping ...
- 83.9k
0
votes
2
answers
122
views
Explain how shall we get a direction at a point on the surface of earth other than north pole using magnetic compass [closed]
The Qibla Compass can give the direction towards "some points on earth" other than north pole, eg : Mecca.
Wikipedia first paragraph, last two lines :
To determine the proper direction, one ...
- 29.8k
1
vote
1
answer
384
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whats happening when i do arctan? Mistake or wrong in calculator
I have a problem in a solids course about mohrs circle and its principal forces.
I have solved to its last part and it all checks up when putting the right angle theta which makes the shear stresses ...
- 985
1
vote
0
answers
56
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Doubt about Malus Theorem. (Optics)
I'm reading the text "General theory of rectilinear ray systems"
By E. E. Kummer. (http://neo-classical-physics.info/uploads/3/0/6/5/3065888/kummer_-_rectilinear_ray_systems.pdf). I'm new in ...
- 39.7k
2
votes
0
answers
53
views
Optical path of a light ray reflected from two mirrors and into a pinhole camera
I have been staring at this problem for longer than I would like to admit.
I am trying to determine the path of a light ray from an object that is reflected from two plane mirrors and into the ...
- 21