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Questions tagged [physics]

Questions on the mathematics required to solve problems in physics. For questions from the field of mathematical physics use (mathematical-physics) tag instead.

This tag is for questions on the mathematics required to solve problems in physics and should not be confused with those on physics concepts. Pure physics questions should go in the Physics Stack Exchange. For questions in the field of mathematical physics, please use the tag instead.

5951 questions
20
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What is the resistance between two points a knights move away on a infinite grid of 1-ohm resistors

On an infinite grid of ideal one-ohm resistors, what's the equivalant resistance between two nodes a knights move away? (please fix the tags, I didn't really know where to put it)
alexanderpas
  • 477
13
votes
2 answers

"Curled-up dimensions"?

I'm a grad student in math, but I don't know as much about physics as I should. I've read a handful of pop expositions of string theory, and they often refer to "curled up dimensions" and I've always wondered what this means. Is this referring to…
Mark G
  • 133
10
votes
1 answer

Mathematicians conceived of black holes long before astronomers actually found any?How?

I read this statement in Lockhart's - "A Mathematician's Lament". But how could mathematicians figure out something like black holes even before astronomers noticing any of them?
eminemence
  • 203
9
votes
2 answers

What is dimensional consistency, mathematically?

When going through symbolic calculations involving physical measurements, it's common to check that the final result is dimensionally consistent. (If I'm calculating a frequency, I'd better get something with units 1/s in the end.) Mathematically,…
blah
  • 820
8
votes
1 answer

Finding time with given distance and acceleration. Help Needed

A plane accelerates from rest at a constant rate of $5.00 \, \frac{m}{s^2}$ along a runway that is $1800\;m$ long. Assume that the plane reaches the required takeoff velocity at the end of the runway. What is the time $t_{TO}$ needed to take off? I…
Lisa Paima
  • 121
6
votes
3 answers

Calculate initial velocity to reach height Y

I am working on a program that shoots a projectile straight up into the air. I need to be able to calculate the initial velocity required to reach height Y. Assume there is a gravitational constant of -9.8m/s and we are dealing with real time. What…
Shijima
  • 163
6
votes
3 answers

Dimension in mathematics and physics

I have studied linear algebra and commutative algebra, there are two kinds of dimension there : the vector space's dimension and the Krull dimension. Also, in physics, dimension is also a very intuitive concepts. My question is : What is the nearest…
trequartista
  • 1,359
6
votes
2 answers

Method of image charge for ellipse

If we put an external electron outside a elliptical metal described by: $$\frac{x^2}{a^2}+\frac{y^2}{b^2}=1$$, how do we determine the image charge or charges of that electron inside this ellipse?
Rob
  • 1,203
5
votes
2 answers

Why do physics books perform this "trick" in integration?

I have the following question, because general physics books like Sears and Serway and others, if not the vast majority, simplify differentials when integrated. Formally I interpret that this is justified by the first fundamental theorem of…
Josue Furiano
  • 57
5
votes
2 answers

Volume charge density of hydrogen atom

The potential of the hydrogenatom is given by: $$\phi(r) = \frac{1}{4 \pi \epsilon_0} \frac{e}{r} ( 1 + \frac{r}{a_0}) e^{-\frac{2r}{a_0}}$$ I'm no supposed to find the volume charge density $\psi$ which produces such a potential, which conceptually…
user80944
5
votes
3 answers

Deriving an equation for the orbital period of a satellite

I'm combining three equations from my physics text book: Newton's law of gravitation: $F = -\frac{GMm}{r^2}$ The centripetal force equation: $F = \frac{mv^2}{r}$ The equation for the speed of an object traveling in a circle: $v = \frac{2 \pi…
Todd Davies
  • 225
5
votes
1 answer

WANTED: Short proof for challenging identity

I have to prove the following without any use of further mathematical theories except basic calculus and linear algebra: Let $ \ell $ be a positive integer and $A$ a real, symmetric and positive definite $n \times n$-Matrix (square Matrix with $n$…
a1337q
  • 379
5
votes
1 answer

Time to take for water to cool down.

My question refers to the cooling of water in a well-insulated , cylindrical cup that is opened at the top. $0.336$Kg of water at $84$C$^\circ$ is poured into the cup which is left to stand on a table at an ambient temperature of $25$C$^\circ$. The…
Jack
  • 53
5
votes
2 answers

Two Dimensional Ising Model and Hamiltonian.

In the Hamiltonian formalism of classical mechanics is well known that Hamiltonian function has several properties with physical interpretations. When I speak of Hamiltonian'm talking about the `` natural'' Hamiltonian of n particles with index $ i…
Elias Costa
  • 14,658
4
votes
1 answer

The Bowed Metre Stick

This problem is being discussed on the AAMT email discussion list. I have a meter long metal ruler. I push the ends together so that they're only 99cm apart, which means the ruler will bow a bit. How tall is that arc? The problem we haven't been…
Rex Boggs
  • 159
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