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Channel: Classical Physics

Model rocket physics: Why doesn't the motor go through the nose cone?

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For those who have built those small model rockets, please help me understand a very very simple physics problem that i for some reason do not fully get.
Why is it that the motor tube does not have a retention ring on it, to prevent the motor from flying out the nose cone? i know it cant be...

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Independence of Trace-Partition function

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I am trying to calculate the partition function of the system of two completely decoupled systems. Probability-wise, the decoupled nature means that the PDF is the product of the PDF of each subsystem. I just wanted to be sure that it would translate into:

$$
H = \sum_{k_i...

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Amplitude of the maximums in single slit diffraction

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Hello!

I was trying to calculate the amplitude of the secondary maximums in the single slit diffraction.
When I use the formula:
$$ I = I_0 (\frac {sin(\Delta \phi /2)} {\Delta \phi /2})^2 $$
If I take ## x = \Delta \phi /2 ## and derivate I get that the maximum occurs when:
$$ x = tan(x) $$...

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Mercury as a plasma at 150 Kelvin

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I was reading up on a theoretical engine employing the following, “Mercury plasma pressurized at 250k atmospheres, at a temperature of 150 degrees kelvin (-123° C), and swirled within its accelerator to 50k RPM.”

Does pressurizing mercury so much somehow allow a plasma to form at such sub-zero...

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Is Information a conserved quantity or not?

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I've been wondering about statespace. Classically, we assume statespace is infinite (presumably so that we can depend on smooth, differentiable manifolds). But even in quantum, we assume a smooth space and time on which we define wave functions and operations (at least in undergrad quantum...

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Contemplating Gyroscopic Forces for fighting robot weaponry

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The premise is that whenever you watch Battlebots or Robot Wars, there's usually a robot on there which has a vertical drum spinner which weighs half the robots weight and spins at thousands of RPM, and whenever the robot turns, it cocks one wheel in the air due to the gyroscopic forces at play...

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Velocity of The Plug

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A problem I was thinking about when talking about natural circulation in a closed loop in another thread:

What is the velocity of the buoyant plug? The loop is filled with water. There are no viscous forces acting on the plug or in the flow. The flow is assumed incompressible.

1679072187705.png...

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Equations for Spherical Resonators

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I host freely for the public a web app for determining the diameter of a sphere to resonate a given frequency and sound hole diameter and length, and then download a stl file for 3D printing. I've realized it has some issues and part of it is the equations i use to determine the sphere's...

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Radiation back reaction in classical electrodynamics

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I've been doing some research on the topic of radiation reaction force/self force in classical electrodynamics and although there are some discussions on the internet I would like direct answers to these following questions:

  1. Is there a rigorous and universally accepted treatment of...

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Negative pressure in a car to power it

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My father has an idea is powering vehicle using negative pressure. I'm trying to explain to him that I don't think that can work. He is saying that imagine you're in space and you try create negative pressure by keep on removing and the only thing that's preventing the collapse of the material...

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Euler vs. Tait (steady precession vs... what?)

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Good Morning

When one studies body rotations, there are two general approaches one uses: Euler Angles vs. Tait-Bryan Angles.

The significant difference is that:
  • Tait–Bryan angles represent rotations about three distinct axes (e.g. x-y-z, or x-y′-z″): Yaw, Pitch, Roll
  • Euler angles use...

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Direct and reverse current

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What is it's benefit?

Deriving Non-linear acoustic wave models, equilibrium state assumption

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The standard derivation in obtaining a single wave equation involves making use of the heat equation with a Taylor expansion of the equation of state, then differentiating this equation and the continuity equation with respect to time, and combining with the divergence of the NS equation...

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Air tank PSI and cubic feet calculation help please

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If I have a air tank that is 1 cubic feet with the pressure gauge at 0 and I pump in air to 5000 psi how many cubic feet of a 100 psi would be in that tank? Any help would be appreciated

Pickleball Physics -- Player reaction time vs aging

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Out of curiosity, how fast are the hands of the pros? I have timed an exchange between BJ/ALW and JD/JI that occurred at the Baird PPA in September 2022. The ball made the (about) 14 foot trip 11 times over 4.0 seconds, for an average trip time of 363mS (milliseconds). (Average speed of 26.3...

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Magnetic bound state in classical mechanics

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Seven years ago, I wanted to share and discuss my experiments results there but it was not possible since there was no published peer review paper yet and apparently not fulfilling forum requirements. Now we have such a publication, but still not sure the subject can be discussed here. Anyway...

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Thoughts about coupled harmonic oscillator system

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Same instruction was given while finding value of 'g' by a bar pendulum.
In the former case,does the spring obeys hooke's law while it forms a coupled harmonic oscillator system?Does the bar pendulum somehow breaks the simple harmonic motion(such that we can't apply the law for sumple harmonic...

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At what level will the water settle in this system?

Limitation of using "post office box" to measure high or low resistance

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Why meter bridge is chosen over post office box to measure low resistance?

Can angular motion exist outside of a gravity field?

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I can't find the answer anywhere here's my question. can a centrifuge exist outside a field of gravity. More specifically, in a theoretical void of nothing without stars in view or any point of reference for comparison how could motion like spinning or acceleration exist?

Basic Question about Gauge Transformations

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Suppose we have an action ##S=S(a,b,c)## which is a functional of the fields ##a,\, b,\,## and ##c##. We denote the variation of ##S## wrt to a given field, say ##a##, i.e. ##\frac{\delta S}{\delta a}##, by ##E_a##.
Then ##S## is gauge invariant when
$$\delta S = \delta a E_a + \delta b E_b...

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Realistic steering wheel angle when car follows points along a path

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Good morning ,

I managed to simplify the physics of my car with only the centrifugal and traction forces. If I'm in control of it, the realism is acceptable for a city builder. On the other hand, I encounter a problem when the car follows an array of points.

2.jpg

The path of the car...

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Archimedes Principle - A Rock and Water Magic Trick

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I understand how to measure specific gravity of a rock. One weighs the rock then tares a beaker of water and then suspends the rock on a string to observe the “weight” gain of displaced water. My brain however could never get how, without adding a drop more water or adding the mass of the rock...

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How do fields retain their uniformity with interposing objects?

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Why don't interposing objects interfere with the integrity of a field's energy between the source and its absorber?

For example, the Sun's gravitational field spreads uniformly through space. If there are interposing objects like Mercury or Venus between the Sun and the Earth, why don't they...

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Transmission Line EM Wave vs EM Wave in Free Space

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According to Maxwell’s Equations, the speed an EM plane wave in free space, far from its source, is determined by the electric constant, ε0, and the magnetic constant, μ0, such that c = 1/√( ε0 μ0).

The units of ε0 are capacitance per unit length and the units of μ0 are inductance...

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Interpreting light as Maxwell's EM wave

Determination of electron temperature in an ion source

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How to correctly determine the temperature of electrons in an ion source based on ECR?
Is it possible to use the Saha equation?
##\frac{n_en_i}{n_a}=\frac{g_eg_i}{g_a}*3*10^{21} T^{3/2} e^{-J/T}##
Using the search, I found the McWhirter criterion for the applicability of the formula above:
##n_e...

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Magnets, Outer space, and Rings

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Awhile back there was a discussion about the following scenario: an astronaut sets free into space outside his window a round magnet so it just sits there a distance away ensuring the spaceship has no effect on the experiment. Then he wafts out gently a large pail of tiny iron filings and dust...

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Reynolds Transport Theorem: differential forms and conserved quantities

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Consider a fluid flow with density ##\rho=\rho(t,x)## and velocity vector ##v=v(t,x)##. Assume it satisfies the continuity equation
$$
\partial_t \rho + \nabla \cdot (\rho v) = 0.
$$
We now that, by Reynolds Transport Theorem (RTT), this implies that the total mass is conserved
$$...

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Moment of inertia and contact force

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Two rotating cylinders are held in contact by a force F1. The force is applied through the center of one of the cylinders. One cylinder is the driving cylinder and the other is the driven cylinder .

Does the moment of inertia of the system depends on the force contact force F1? Why?


And...

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Surface area and length (percent increase relationship)

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Hi all,

While calculating the surface area for an object, I was told the below statement. However, I am not sure is this correct, please can someone help me to explain this with an example? Is the below statement always true?

The surface area % increase should be in line or less than the %...

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Trig functions and the gyroscope

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Good Morning

As I continue to study the gyroscope with Tait-Bryan angles or Euler angles, and work out relationships to develop steady precession, I notice that the trig functions cancel.

I stumble on terms like:

1. sin(theta)cos(theta) - cos(theta)sin(theta)
2. Cos_squared +...

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Why does ##u## need to be small to represent the Taylor expansion

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Necessary condition for a curve to provide a weak extremum.
Let ##x(t)## be the extremum curve.
Let ##x=x(t,u) = x(t) + u\eta(t)## be the curve with variation in the neighbourhood of ##(\varepsilon,\varepsilon')##.
Let $$I(u) = \int^b_aL(t,x(t,u),\dot{x}(t,u))dt = \int^b_aL(t,x(t) +...

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How do I calculate the drop force on a cord and eye bolt?

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i have a question. I have set up an expierment and need some values.
I have a round, 3d printed disk, 0.25 inches thick and 4 inches in diameter. In the center, i have a eye-bolt attached. I have hooked up a chain to the eyebolt and some weight to the chain.
I have 40Lbs hanging right now and...

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Why is gravitational force directly proportional to the product of masses?

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why is that the gravitational force proportional to product of masses why not sum of masses or something else .........

Help with Euler Lagrange equations: neighboring curves of the extremum

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I tried writing this out but I think there is a bug or something as its not always displaying the latex, so sorry for the image.
I have gone through various sources and it seems that the reason for u being small varies. Sometimes it is needed because of the taylor expansion, this time (below) is...

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What is meant by "upper limit of work done on Earth"?

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jgjgjgj.png
I think that the work is meant to be work done for instance in power stations. Or is it similar to work I do on a body when I lift it for example? But how can we then do that work on our Earth? I just need to understand the task, otherwise I want to solve it myself.

The problem...

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How is it possible for two waves to be in phase when they have different amplitudes?

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May I know how is it possible for two waves to be in phase when they have different amplitude? I couldn't find any existing graphs that clearly shows how the two waves are in phase, would anyone be able to sketch it out so I can have a look. Thank you:smile:

Equalizing airflow through multi-hole orifices

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I know the Bernoulli equation for calculating the air velocity through a pressurized hole, but I am wondering if one hole of a given area behaves the same as multiple holes with the same total area. The Bernoulli equation doesn't make a distinction.

Background: As a personal 3D design and...

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Vector calculus: line element dr in cylindrical coordinates

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We were taught that in cylindrical coodrinates, the position vector can be expressed as
IMG-20230422-WA0029.jpeg

And then we can write the line element by differentiating to get
IMG-20230422-WA0031.jpeg.

We can then use this to do a line integral with a vector field along any path. And this seems to be what is done...

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Measurement uncertainty due to thermal noise

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I have a charged particle in a Penning trap. The particle motion is non-relativistic and the energy is high enough such that we can assume it is not in the quantum regime. For the purpose of the question I am interested only in the axial motion of the particle, so basically this is a classical...

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v=ds/dt, a=dv/dt: vdv=ads

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In an introductory dynamics textbook, we often see this progression

v = ds/dt ---> dt = ds/v

a = dv/dt ---> dt = dv/a

Equating the dt, we get: vdv=ads

Now my question

On the one hand, this works for certain problems.
On the other hand, this is splitting the differential.

Could...

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Virial theorem and translational invariance

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According to the virial theorem,

$$\left\langle T\right\rangle =-{\frac {1}{2}}\,\sum _{k=1}^{N}{\bigl \langle }\mathbf {F} _{k}\cdot \mathbf {r} _{k}{\bigr \rangle }$$
where ##N## is the number of particles in the system and ##T## is the total kinetic energy. It is often claimed that this...

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Rolling Motion direction of Velocity center of mass

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Hi I have come across something confusing in rolling motion. If an object moves with a positive V_cm meaning to the right its angular velocity will be clockwise or negative. The formula is V_cm=wR but for a positive V_cm you get a negative w as it moves clockwise if V_cm is to the right...

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Mass dropped onto rotating disk

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Picture a flat disk of radius r with a radial vane. The disk is rotating at angular velocity w. Assume the vane is straight, starts at the center and ends at the perimeter of the disk.
A very small round mass ( of m grams) is dropped onto the disk very near the center. The...

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Forces on rotating disk object

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Forces on rotating disk object
Hi. Is it convenient to ask following question.
Suppose we have solid circular object and 5 different moments
like in the picture:


Rotating.jpg


In moment 1 we apply force (downwars direction) so as to start rotating the object around center of
the mass...

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How long does it take to reach harmful CO2 levels in a room?

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• I exhale 1 kg of CO2 per 24 hours = 41.67g/h (average)
• Co2 indoors after ventilation = outdoors = 400 ppm (world average)
• Co2 indoors threshold = 1000 ppm (cognitive effect)
• Room volume = 32.5 m3
• Details to neglect: window and door closed tight, no HVAC system...

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Neil DeGrasse Tyson on "sharing water" with historical figures

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Hello,

I've heard versions of these statements (below) from other scientists, but I've never seen anyone break them down. Do molecules in air really move (diffuse?) their way around the entire globe, or are there localized "pockets" that really don't move that far from home? Intuitively, water...

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Are equations of motion invariant under gauge transformations?

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We know that all actions are invariant under their gauge transformations. Are the equations of motion also invariant under the gauge transformations?

If yes, can you show a mathematical proof (instead of just saying in words)?

How does wind affect a turn for an aircraft?

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First, I understand how wind effects aircraft tracking. I can do the calculations involving wind correction angles, effects on ground speed, headwind or tailwind calculations, etc. I teach it in a college piloting program.

I am wondering how the ground tract of turn is effected by the wind...

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