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Questions tagged [geometry]

To be used for questions on geometry closely pertaining to physics. Includes differential geometry and Euclidean geometry. Do prefer the more specific tag differential-geometry for questions about differential geometry.

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Conception of earth's size based on the width of the observable horizon when standing at sea level and the circumference of the earth

As an aid to conceiving of the size of the earth, using the information that the horizontal (left to right or right to left) width of (not the distance to) the observable horizon when standing at sea ...
Sketcher's user avatar
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1 vote
0 answers
63 views

Discovery of a Formula for Geostationary Orbit Distance: Seeking Expert Feedback [closed]

I’m an amateur enthusiast without a formal academic background in mathematics or science. Recently, I stumbled upon an idea and derived a formula that I believe calculates the distance traveled along ...
Luca Blonda's user avatar
0 votes
1 answer
51 views

Throwing a ball in the air

When we throw a ball in the air, we know that if we do not throw it too high, then g can be held constant over the trajectory and we can approximate the curve by a parabola. However we also know that ...
tensorman666's user avatar
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0 answers
61 views

Einstein's notion of "covariant"

In his The Meaning of Relativity, pg. $11-12$, Einstein explains the notion of "covariant" along the following lines: Consider a point $\mathbf x$ on a straight line $\mathbf x -\mathbf A=\...
Awe Kumar Jha's user avatar
2 votes
0 answers
49 views

Potential of circle and $n$-gon

Consider power central fields $f \sim r^k, - \infty < k < \infty$, and unit circle, "charged" in the sense of the field. We will be interested in the potential within the circle, i.e. ...
lesobrod's user avatar
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3 answers
65 views

Why does moment of inertia stop at 1/2 as solidness of a cylinder increases?

So I have two things about moment of inertia: The I for a hoop is $I=MR^2$ and the I for a solid disk is $I=\frac{1}{2}MR^2$ I've noticed that as "solidness" goes up from 0% (completely ...
Shelby Longbottom's user avatar
1 vote
1 answer
49 views

Finding Exterior Confining Pressure from Interior Pressure Point for a Solid Disk

Essentially, I've been wrapping the pictured object tightly with string to exert a confinement pressure on its exterior. It's been difficult however to make a good estimate of how much pressure is ...
Modestas Botha's user avatar
5 votes
3 answers
504 views

Is obeying the parallelogram law of vector addition sufficient to make a physical quantity qualify as a vector?

I know that obeying the parallelogram rule of vector addition is a necessary condition for vectors. But is it sufficient? In other words, can there be a quantity that is added using the method but ...
HerrAlvé's user avatar
  • 379
25 votes
9 answers
6k views

Why are spherical shapes so common in the universe?

I have a simple question. Why are most objects in the observable universe spherical in shape? Why not conical, cubical, cuboidal for instance? I am furnishing a few points to justify this statement: ...
Ishaan's user avatar
  • 517
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0 answers
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Describing force accumulation trend of an infinite volume with evenly distributed radiative sources

I am looking for confirmation if I've built my equation properly. My goal is to describe the change in force over time at a given point if evenly distributed radiators (in-phase or cumulative energy/...
WhetScience's user avatar
5 votes
0 answers
199 views

Modified Special Geometry of SUSY Moduli Space

It is known that the Coulomb branches of 5d $\mathcal{N}=1$ and 4d $\mathcal{N}=2$ SUSY (both have eight supercharges) satisfy special geometry. This means that there exists a holomorphic prepotential ...
TwoStones's user avatar
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0 answers
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Is displacement vector always the shortest path?

I read that the displacement vector of a particle is the shortest path between its initial and final positions since it's a straight line joining the two points, this holds true for me till a 2D ...
Manish's user avatar
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8 votes
2 answers
849 views

Why are material properties often described by symmetric tensors?

It seems to me that whenever there is some material parameter for a continuum, it is described by a symmetric tensor. This is the case for the mechanical stress tensor, permittivity of crystals, the ...
Kotlopou's user avatar
  • 381
19 votes
3 answers
5k views

Does the top of a wheel really move at twice the velocity of the center?

According to the physics of a wheel rolling without slipping, the topmost point moves twice as fast as the wheel. But I tried an experiment: Take a wheel on a table and hold a ruler horizontally in ...
Manukrishnan P's user avatar
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1 answer
70 views

Doubt in pitch of screw gauge [closed]

I have just started learning about screw gauge and I came across this statement about pitch The pitch is the distance between two consecutive threads of a screw which is equal to the distance moved ...
Dhyaneshwar's user avatar
-1 votes
1 answer
101 views

Geometry of spacetime at different length scales [closed]

Does spherical geometry govern physics at the quantum scale? My motivation for this question came from studying non-Euclidean geometry. When we go down from general relativistic length scales to ...
tony schofield's user avatar
21 votes
9 answers
5k views

Is there such a thing as a "physical" fractal?

The recent discovery of a molecule that mimics the Sierpinski gasket has spurred headlines identifying it as the first fractal scientists have found in nature. I find these claims highly dubious ...
starseed_trooper's user avatar
5 votes
4 answers
1k views

How do parallel reflected rays meet to form image at infinity? If they never meet then how is image formed?

In my textbooks it is written that when an object is kept at focus, its image is formed at infinity and is real. But how is this possible because parallel lines never meet and it is necessary for rays ...
Shivam Gogia's user avatar
0 votes
2 answers
62 views

Average Speed in one half of an elliptical orbit

I was wondering whether the average speed along one half of an elliptical orbit (say in a star planet system) had a closed form exact solution using Kepler's laws. My approach was using the ...
Echelon96's user avatar
1 vote
1 answer
96 views

How can I see Orion's Belt in winter and summer?

How can the 23 degree tilt of the Earth enable someone in Argentina to see the same constellation (Orion's Belt) in winter as someone in Britain in summer?
Danny Rosenberg's user avatar
13 votes
4 answers
1k views

How do we measure the position of a body? [duplicate]

I am a high school student and I was studying kinematics about position of a body. So, one thing I do not understand in this diagram is the position of woman. Initally, at $t=0$, this woman was at $...
Armadilo's user avatar
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0 answers
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Collection efficiency of mirror

I want to compare plane and parabolic mirror for collection of photon from a point source. Intuitively, parabolic mirror focuses all rays from point source and gives parallel rays therefore has a ...
Sneaxx's user avatar
  • 1
4 votes
0 answers
216 views

Does the term $d ( \omega_{ab} \wedge \theta^a \wedge \theta^b )$ have any significance?

If $\omega_{ab}$ is the spin connection 1-form, and $\theta^a$ are the tetrad 1-forms, then one has the equality \begin{equation} \int \, d ( \epsilon_{abcd} \omega^{ab} \wedge \theta^c \wedge \theta^...
user1379857's user avatar
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2 votes
1 answer
113 views

Why is the refractive index for light rays travelling in circular paths proportional to $1/r$?

While studying optics, I came across a problem with solution in which the trajectory of light rays was known—circular paths around a fixed point in space, and the question was that of determining the ...
davidaddisonsenjaya's user avatar
0 votes
0 answers
68 views

Finding the limiting refractive index of a rainbow

Give the limiting refractive index of a rainbow. The raindrops are modelled as spherical droplets, with refractive index $n$, with parallel rays from the Sun incident on it. I have a very limited ...
Developer's user avatar
0 votes
2 answers
75 views

Confusion about breaking apart vectors

Hi I've probably got a very basic question but I'm really confused about this. If I have a vector that starts at the origin and points to say (3,-3) so the 4th quadrant, and I am wanting to split ...
Lauren 's user avatar
40 votes
5 answers
9k views

When a bus goes around a corner, does the person sitting at the back travel further distance than the person sitting at the front?

This is a bit of childish question. When a bus goes around a corner, does the person sitting at the back travel further distance than the person sitting at the front? My thought is no because the bus ...
StimMarine's user avatar
0 votes
0 answers
14 views

How to approach a static analysis when objects are on differing inclines?

I think this sort of problem is known and relatively simple when on a single angle of incline, but I'm trying to understand a problem with two points of contact of a uniform vehicle where each contact ...
kilxi's user avatar
  • 1
0 votes
3 answers
56 views

Is the radius equal to length/radians? [closed]

Is the radius equal to the length/radians. Since the circumference is 2 pi times r and radians of an entire circle is 2 pi r should be equal to lentgh/radians I needed this proof to understand why we ...
Thedambamjam's user avatar
0 votes
4 answers
135 views

How can a triangle have a sum exceeding 180 degrees in a curved space?

I was reading a book to understand the limits of the euclidean space I understand that lines that are parallel in 2d can meet in 3d space like on a sphere but it is hard to imagine or fathom why the ...
lodo's user avatar
  • 33
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0 answers
55 views

Determine the equation of earth's orbit

I am trying to find the the equation earth's orbit using Kepler's Scheme. After every 1.88 years Mars returns to its initial position in the sky. With reference to the diagram and data below find the ...
sameed hussain's user avatar
-2 votes
2 answers
91 views

In real life, we can have a pencil of length 2 cm. Can we have pencil of length $\sqrt{2}$ cm? [duplicate]

In real life, we can have a pencil of length 2 cm. Can we have pencil of length $\sqrt{2}$ cm? My answer to that was no , we cannot even make 2 cm pencil. My argument was that when are working ...
user avatar
0 votes
0 answers
43 views

Why is time taken to go around the Sun to cover a small fixed angle proportional to the square of the distance?

I am reading Feynman's lost lecture. At this point, he asks us to consider points J, K, L and M which subtend equal angles at the sun S. And then he claims that triangles JKS and KLS are similar ...
Neeladri Reddy's user avatar
3 votes
2 answers
456 views

Geometry of anticommutation relations

I am asking this question as a mathematician trying to understand quantum theory, so please forgive my naivety. Systems satisfying the canonical commutation relations are naturally modeled with ...
Cole Comfort's user avatar
0 votes
0 answers
31 views

Carbon Nanotube Modeling

In various references, we see the construction of unit cells of carbon nanotubes from chiral and translational vectors. The chiral vector is given as: $$\vec C_h = n\vec a_1 + m\vec a_2$$ While the ...
benjamin_ee's user avatar
0 votes
1 answer
31 views

Does anyone know of published data on Mach interactions with various asymmetrical toroids?

I was looking for any lab conducted tests, or computer models of Mach reflections off of different toroids. How would shock waves propagate through asymmetrical 180° ring toroids, what kind of ...
-1 votes
1 answer
81 views

How fast do I have to fly vertically up to pause sunset?

I'm standing on the famous Laguna Beach in southern Los Angeles to watch the sunset on December 18th (33.541679°N 117.777214°W, 0m elevation, 16:44 PST). Now, from my perspective at the shore, the sun'...
Richard Zhu's user avatar
2 votes
0 answers
61 views

How much of an observer's field of view will be black upon crossing an event horizon? [closed]

The aberration of light will cause an observer to still see a black hole as "distant" when the event horizon is crossed. This means that if the observer looks directly toward the center of ...
Patrick O'Brien's user avatar
1 vote
1 answer
70 views

About Plane motion [closed]

An excerpt from a book I read: “In reality, objects are moving in a 3-dimensional space. However, if the acceleration of the object is constant, then there must be a certain plane which contains the ...
Samuel Tse's user avatar
23 votes
1 answer
7k views

Based on my calculations, we cannot see the Earth from the ISS. Obviously it's wrong. Why?

What started as a fun exercise really annoys me because I cannot see where I got it wrong. I initially wanted to see how many photons hit a pixel of a camera on the ISS pointed at the Earth - but I ...
Mister Mystère's user avatar
2 votes
4 answers
488 views

Is buoyancy affected by container geometry? [duplicate]

Is it possible for something that can't float in a rectangular container to float in a triangular container?
Mason Valentine's user avatar
1 vote
0 answers
82 views

Similar to how there's field lines that make equations in Newtonian Gravity more intuitive, is there something that makes GR equations more intuitive?

One way I know to get intuition for the derivation of the force equation $$F=\frac{GM_1M_2}{r^2}$$ in Newtonian Mechanics is to imagine gravitational field lines, in combination with certain ...
Anders Gustafson's user avatar
0 votes
0 answers
66 views

What is heard when a tuning fork is struck?

When a tuning fork is struck I hear two tones. From a distance I can hear a high octave frequency of the pitch of the tuning fork. Though, if I listen to it closely (closer to my ears), I also hear a ...
Lecifer's user avatar
  • 109
1 vote
1 answer
43 views

Is it possible for 4 satellites cannot render a position fix on Earth?

I recently learnt about how GPS works and how it uses the intersection of spheres to locate a person which got me thinking whether 4 spheres can always guarantee a position fix. My understanding is ...
Nullity's user avatar
  • 25
2 votes
1 answer
200 views

Is the celestial sphere we actually see the Riemann Sphere?

I've been watching a few lectures by R. Penrose where he seems to say that what we see around us is the Riemann sphere. He usually gives the example of an observer floating in deep space or if the ...
Svenn's user avatar
  • 31
0 votes
0 answers
59 views

Distance between lattice planes of a lattice with two different atoms

I know that the distance between two adjancent lattice plane of the same family is given by $$d=\frac{a}{\sqrt{h^2+k^2+l^2}}$$ if we use the conventional cell of a cube with volume $a^3$. I also know ...
Michael's user avatar
  • 129
1 vote
2 answers
126 views

The difference in path lengths for waves in the double slit experiment

Fig.1 I don't quite understand the diagram, because it shows $L_1$ and $L_2$ as parallel, even though they are supposed to meet at the same point. I believe the idea is that $\Delta L$ approaches $d \...
user110391's user avatar
-1 votes
2 answers
441 views

$r_1+r_2= A$ in prisms

In class we derived a result which said that the sum of the 2 angles of refraction in a triangular prism $r_1+r_2$ is equal to the angle of the prism $A$. The proof goes like this Over here, it is ...
Pumpkin_Star's user avatar
1 vote
1 answer
56 views

Tetrahedral Geometry and Potential energy

Intuitively, I'd think it possible to use potential energy to find the bonding angles in methane, but I'm not getting the right answer. Am I missing something? In a tetrahedral, the faces are ...
R. Romero's user avatar
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0 votes
1 answer
116 views

The Plus/Minus sign on Forces in a Cartesian coordinate system

I have been struggling with Forces in a Cartesian Coordinate System and whether to understand what signs to put on to solve simple problems in the view of mathematics. Let's make a simple one ...
Draginev's user avatar

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