Mathematics Stack Exchange
Mathematics Stack Exchange

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
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Proof that $\epsilon_{ijk}$ is the same as the determinant of the Kronecker delta

I just learned about the Kronecker Delta function and $\epsilon_{ijk}$ for the first time, and I still can't wrap my mind around how to prove that $$\epsilon_{ijk} = det\begin{pmatrix} \delta_{i1} & \delta_{i2} & \delta_{i3} \\ \delta_{j1} &…
cirko
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The relative momentum

A missile of mass 1 kg is launched with velocity $200$ m/s towards a tank of mass 50 tons moving towards it with velocity 20 m/s . Find the momentum of the missile with respect to the tank . My turn :- $H(\text{missile w.r.t tank}) =…
Hussien Mohamed
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2 answers

Calculate the change in velocity over a given distance.

I am trying to calculate the maximum change in speed over a given distance with a known constant acceleration, current speed and of course, distance. I do not know the time. However, I run into the issue that the speed is undefined if the starting…
Chase
  • 123
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1 answer

Position, velocity, and acceleration question

An object is $100$ feet above ground and has an initial velocity of $15$ m/s upwards and it is being accelerated by gravity. What is the equation for the height? So right away, I know that it would be $p(t)=100$ when $t=0$ and $v(t)=15$ and…
user612996
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1 answer

Property of a Lorentz transformation

Assume $\mathbf{x}$ to be a lightlike 4-vector in reference Frame $F$ and $\mathbf{x'}$ the corresponding vector in reference frame $F'$ where both frames share the same origin. Then due to the principle of…
jerico
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1 answer

What does a circle in 4d spacetime "look like"?

In the normal metric for spacetime $ds^2=dx^2+dy^2+dz^2-cdt^2$ What does a "circle" of unit distance look like (the set of all points that satisfy $ds^2=1$?) That is does the negative give this any unusual properties as compared to the usual 4d…
shai horowitz
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1 answer

How to find the displacement of the bird?

$\require{cancel}$ I'm not even sure I should post this question here or not, but here we go. A bird is flying to and fro between two cars moving towards each other on a straight road. One car has a speed of $18$ km/h while the other has the speed…
rikusp2002
  • 472
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2 answers

Variable refractive index question

A ray of light travelling in air is incident at grazing incidence on a slab with variable refractive index, $n (y) = [k y^{3/2}+ 1]^{1/2}$ where $k = 1 m^{-3/2}$ and follows path as shown in the figure. What is the angle of refraction when the ray…
Abhishek Kumar
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Two velocities, fixed distance = time taken?

Disclaimer: I am several decades out of school and I feel this is likely very simple. I just want verification. Given a fixed distance $D$. An object moves at speed $A$ $65\%$ of the time, and speed $B$ $35\%$ of the time. What is the total time…
imukai
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Distance to stop given initial velocity, initial acceleration, and maximum jerk

Given an initial velocity $v_0$, initial acceleration $a_0$, and a maximum (positive or negative) jerk $j$, what will be the final resting position $p$ (in relation to the initial position) when coming to a complete stop (velocity and acceleration…
Jordan Woyak
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Determine a formula by knowing a few x,y numbers and the results for each combination

I have an optical corrector that needs to be adjusted to a certain position between a camera and a telescope, the manufacturer provides a table with a few x and y parameters of the telescope that determine that position of the corrector but my…
Christos Oscar Kambiselis
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Is the average velocity of an object going down an inclined ramp equal to the instantaneous velocity of the object at the midpoint of the ramp?

So, I need to verify whether or not the average velocity of an object going down an inclined ramp is equal the instantaneous speed of the object in the midpoint, and I need to figure out a simple way to explain it as well.
Isaac Lee
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Losing-mass oscillator - solving using Laplace transform

Statement of a problem Body of mass $M=m+m_0$ is moved out of balance ($x(0)=A$, $\dot{x}(0)=0$) and is subject to restoration force of magnitude $F = -kx$, where $x(t)$ describes position of body in time. As time passes, body loses mass with rate…
user535260
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2 answers

Calculate stopping distance from deceleration time and speed

Quite a simple question but I'm having issues - I have the speed of an object (say 5m/s) and the time it takes the object to come to a complete stop (say 2s). I want the object to stop exactly on a given position (T). At what distance from T will I…
EmmetOT
  • 141
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Setting a moving projectile's acceleration so it goes through the origin

Scenario: Suppose there is a projectile traveling in two-dimensional space. It is currently at point $(p_x, p_y)$ and has velocity $(v_x, v_y)$. It can accelerate in any direction but the magnitude of its acceleration must be $m$. Goal: I want to…
Blavius
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