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Questions tagged [vibrations]

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442
votes
4answers
53k views

Can I compute the mass of a coin based on the sound of its fall?

Other day, I bumped my bookshelf and a coin fell down. This gave me an idea. Is it possible to compute the mass of a coin, based on the sound emitted when it falls? I think that there should be a ...
104
votes
7answers
19k views

Why do tuning forks have two prongs?

I believe the purpose of a tuning fork is to produce a single pure frequency of vibration. How do two coupled vibrating prongs isolate a single frequency? Is it possible to produce the same effect ...
29
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4answers
10k views

Why does a large train cause the ground to shake?

I work in a 4 story building that is approx. 150 feet away from a set of train tracks. When a large (40+ car) freight train goes by, the shaking in the building is perceptible. As I've watched the ...
26
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3answers
24k views

Theory behind patterns formed on Chladni plates?

In this video of vibrating Chladni plates we can see small sand particles align themselves into different interesting patterns (also shown in the image below) which correspond to some particular ...
23
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2answers
1k views

Vibrational anharmonic coupling and noise-induced spontaneous symmetry breaking in a hexagonal finite mechanical lattice

Happy holidays, everyone! The following is part question, part visual gallery, and part classical mechanics problem. Inspired by snow over the weekend I began simulating the vibrations of the ...
21
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3answers
3k views

Non-resonant but efficient frequencies

I understand that if the frequency of a driving force coincides with the natural frequency of an oscillator (say a pendulum), the rate at which energy is transferred to the same is maximized. However, ...
19
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2answers
3k views

In counting degrees of freedom of a linear molecule, why is rotation about the axis not counted?

I was reading about the equipartition theorem and I got the following quotations from my books: A diatomic molecule like oxygen can rotate about two different axes. But rotation about the axis down ...
16
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2answers
3k views

Can the vibrations from the Earth affect gravitational wave detectors?

I was very interested in gravitational wave detectors and how they work exactly. From what I know they set up two lasers with mirrors set up to cancel each other out. Then if movement is detected from ...
15
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2answers
2k views

Why does vibration loosen screws?

I am trying to figure out why vibrations (say, from an engine) loosen screws. It seems to me that there is evident symmetry between loosening and tightening a screw. I am wondering what breaks this ...
15
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3answers
642 views

Similarity between Schrodinger and Euler-Bernoulli equations - any possible physical meaning?

I noticed a long time ago the similarity between Schrodinger equation and Euler-Bernoulli beam equation. Namely, Euler-Bernoulli equation is equivalent to the system of Schrodinger equation for a free ...
13
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5answers
9k views

Why do harmonics occur when you pluck a string?

When you energise a taut string, the following resonant modes of vibration occur: Plotting on the frequency domain, you can see their corresponding frequencies: But what is the underlying physical ...
13
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3answers
3k views

Why don't metals damp vibrations?

Fluid damps vibrations due to viscous dissipation. Does anyone has any insight on a molecular, microscopic level about the reasons that vibration damping of metals is negligible?
10
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4answers
3k views

If all harmonics are generated by plucking, how does a guitar string produce a pure frequency sound?

A guitar is a plucked instrument and it is played by plucking a string at an off-centre point fixed at two ends. In general, Fourier analysis tells that all harmonics (the resonant frequencies of the ...
10
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3answers
2k views

Will a violin string keep vibrating for a longer time in vacuum than in air?

Hitting a string of a violin or a guitar will cause that string to vibrate, but after short time the amplitude of the vibration will decay, consequently the produced sound will die out. I suppose ...
9
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2answers
2k views

Why does a metal block make a shrill sound but not a wooden block upon hammering?

When hammered, a metal block makes a shrill sound but not a wooden block of identical shape. Is it that the wooden block vibrates with lesser frequency than the metal block? If so, why is that? Also ...
8
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5answers
3k views

Does plucking a guitar string create a standing wave?

About two weeks ago there was a mock test in Korea, and a physics question asked if a plucked guitar (it was actually a gayageum, a traditional instrument, but I'll just call it a guitar for ...
8
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1answer
216 views

How does a guitar work?

Here are four different possible ways: The plucked string vibrates longitudinally, vibrating the air around it. This vibrating air then causes the air inside the sound box to vibrate also, which ...
8
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3answers
383 views

Why choosing for prime numbers eliminates vibration?

I have read that the spokes of a car wheel are usually five because, besides other substantial reasons, five being a prime number helps to reduce vibrations. The same also happens with the numbers of ...
8
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2answers
305 views

Picking up audio using high speed video?

In the movie Eagle Eye, ARIIA (an intelligence-gathering supercomputer/AI) picks up audio using video recording of the vibrations in a coffee cup. How close is this to reality? I have see it done ...
8
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1answer
386 views

Equations of motion of displacement field

We have an action: $$S[\boldsymbol{u}] = \frac{1}{2} \int dt \int d^3x \left\{ \mu (\frac{\partial u_{i}}{\partial t})^{2} - \nu (u_{ii})^{2} - \rho(u_{ij})^{2}\right\} $$ Where $u_{ij} = (\partial_{...
7
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2answers
2k views

Why sound does not heat up the air?

Both thermal energy and air are propagated through vibration of particles so why sound does not heat up the air e.g loud musical instrument does not generate much heat ?
7
votes
1answer
229 views

Specific heat capacity vs KE gain of particles

To increase the temperature of 1kg of water by 1C you need 4200J of energy. However, the KE gain is only $\frac{3}{2} k_B \Delta T \cdot 6.02\cdot 10^{23} \cdot \frac{1000}{18} = 692.3$J. Where does ...
7
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2answers
184 views

vibrating charged string

I know how to calculate the electric field generated by a charged string at rest. And I know how to calculate the vibrations of a (not charged) string with given boundary and initial conditions. All ...
6
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3answers
9k views

Difference between sound and heat at particle level

If heat (or thermal energy) are vibrations of particles and sound is a wave that is propagated through medium e.g vibration of air particles, what indicates if vibration of particles will be perceived ...
6
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3answers
7k views

Why do objects have resonance at natural frequency?

What actually is a natural frequency for an object and what makes it vibrate with increased amplitude when coupled with an external oscillator that matches the natural frequency?
6
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4answers
585 views

What prevents sound to be just wind?

I have two questions about the physics of sound. As a background, I know the process of sound production can be understood as 3 stages that happen continuously: An object oscillates back and forth ...
6
votes
3answers
169 views

Vibrating string as a dynamic system

It's known first order dynamical systems had one energy storage (example C, in RC circuits) these systems act as a filter but don't resonate, on the other hand a second order system had two energy-...
6
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2answers
946 views

Finding the components of the tensor for potential and kinetic energy

I have a rather poor understanding of what a tensor is, but enough to apply it to the biggest part of the classical mechanics I'm studying. However, I've run into a small problem while studying "Free ...
6
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3answers
1k views

Is photon emission possible without electrons changing energy levels?

Does molecular vibrational transition and consequent emission of infrared radiation involve electrons changing energy level? In wikipedia, about vibronic transitions it says "Most processes leading to ...
6
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0answers
103 views

Why are vibrations so common? [closed]

Why are vibrations so common? We all know, or pretend to know, that symmetries and the least action principle lead to conservation laws.Is there something more fundamental behind the fact that ...
6
votes
0answers
517 views

Physical meaning of Laplace-Beltrami eigenfunctions?

The eigenfunctions of Laplace-Beltrami operator are often used as the basis of functions defined on some manifolds. It seems that there is some kind of connection between eigen analysis of Laplace-...
5
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3answers
459 views

Vibration on the guitar when playing two strings

I know that when I am playing one string on the guitar, it creates a standing wave which causes the entire body vibrates in its frequency and therefore create sound waves. But, what about two strings? ...
5
votes
2answers
92 views

Do Baryons have Quantized Vibrational and Rotational States?

Given that baryons are not point particles but are composed of three quarks, are there quantized vibrational and rotational states analogous to those of molecules? If not why not, and if so are ...
5
votes
2answers
634 views

What is torsional vibration?

Specifically, what is happening physically if a metal rod experiences torsional vibration? Googling torsional vibration brings up a load of research papers, well beyond the level I'm at. I can't seem ...
5
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3answers
3k views

Extra vibrational mode in linear molecule

When calculating the number of vibrational modes for a molecule, the formulas differ for linear $(n = 3N - 5)$ and non-linear $(n = 3N - 6)$ molecules, where $n$ is number of modes and $N$ is number ...
5
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2answers
3k views

Frequency of touch, taste, and scent [closed]

So I was thinking about sound - and how anything below 20Hz is basically inaudible to humans (because it is too low of a frequency to be recognized), as well as anything above around 20KHz (because it ...
5
votes
3answers
26k views

What are the first, second etc modes of vibration?

What is the first, second etc mode? I cannot find online explanations. Is it the shape of vibration? Does a thing have more than one natural frequencies (first, second, etc) and it vibrates with ...
5
votes
2answers
60 views

What causes some gas diffusion to be noisy, others to be quiet?

My question is about noise in gas diffusion, specifically when a can of pressurized gas is opened into the atmosphere. I want to know why this is noisy sometimes, but quiet other times. Does the gas ...
5
votes
1answer
40 views

When a skyscraper sways in the wind, in which direction is the motion?

Skyscrapers sway in the wind (Source here). Which direction, relative to the wind, do they sway, ignoring effects of other buildings nearby? I can imagine wind from the North blowing a skyscraper's ...
5
votes
1answer
209 views

Does a hollow sphere vibrate longer than a solid sphere?

Assume the following are constant: Surface area of both spheres The spheres are both made of titanium (Ti). Mechanism that strikes a given sphere delivers the same energy per strike. Spheres are ...
5
votes
2answers
482 views

Degenerate vibrating modes of a metal plate

My question is based around this video: https://www.youtube.com/watch?v=1yaqUI4b974 The video shows sand settling in vibrational nodes of a plate at certain resonance frequencies. It appears that ...
5
votes
1answer
231 views

To what degree does guitar construction affects the vibration of the strings?

There's an old debate going on in the guitar community about how much does wood choice and body shape affect the sound of an electric guitar. No one denies that there's a difference acoustically (how ...
5
votes
1answer
413 views

Energy Conservation of waves at a boundary

Consider a wave traveling on a string with velocity $\upsilon$ and mass density $\rho$ having unit length so that the mass of the string is $\rho$. Considering the string to be a simple harmonic ...
5
votes
2answers
1k views

What actually is the wavevector in the context of phonons and lattice vibration?

When we deal with Electromagnetic waves the wavevector has the meaning that it encodes the information about the direction of propagation, together with the wavelength. In Quantum Mechanics, the ...
4
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5answers
2k views

Why do tall buildings have low resonant frequencies?

I know that tall buildings have low natural frequencies, hence they're more vulnerable to earthquakes, but why do they have low natural frequencies?
4
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4answers
529 views

Understanding Heat

Heat or thermal energy as understood is nothing but motion of molecules of the matter. If the molecules are tightly bound (in case of solids), it is to-and-fro molecular vibrations, otherwise it is ...
4
votes
3answers
157 views

Would a bag of neutrons have temperature?

Neutrons interact with each other only via exchange interaction, while "every-day particles" and their temperatures are governed by electrostatic forces. What are the implications of this difference ...
4
votes
6answers
26k views

What is the significance of the phase constant in the Simple Harmonic Motion equation?

The displacement of a particle performing simple harmonic motion is given by $x = A \sin(\omega t + \phi)$ , where $A$ is the amplitude, $\omega$ is the frequency, $t$ is the time, and $\phi$ is the ...
4
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1answer
4k views

How do I recover the 1D wave equation from the Lagrangian?

Consider small displacements, $y(x,t)$, of an element of a string (circled in red and shown below) from equilibrium. The force balance in the vertical direction yields: $$+\uparrow \Sigma F: -T\sin(...
4
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2answers
78 views

Difference between sound and high temperature [duplicate]

Though vibration is a common concept in sound and “high temperature”, the essential difference between the two is mentioned to be the way the vibration takes place. The former has vibrations that ...