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Questions tagged [vibrations]

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58 views

How do we know that the vibrational eigenmodes of a system are able to fully describe all possible motions of the system?

In the classical case of identical masses coupled with springs, in a 3D lattice like structure. The equations of motion with the harmonic approximation are given by: $$M\ddot{u}_{m}^{\alpha} = \sum_{...
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2answers
312 views

Amplitude of oscillations in non-resonant forced vibrations

I am somewhat confused about the amplitude of forced vibrations at non-resonance driving frequencies. If I was to assume that there was no / negligible damping present, then at resonance, the ...
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2answers
85 views

Constraints on digital mp3/wav sound reproduction?

A recent tv broadcast on http://www.cuny.tv/ discussed a new and successful business startup in new york city selling vinyl LP's. Sorry, I can't find that episode, but I think it's this company http://...
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1answer
250 views

String vibration and damping

In case of a home experiment about string vibration under the boundary condition $$y(l,t)=y(0,t)=0$$ Where $y=$ the displacement of the string at spatial co-ordinate $x$ and at time $t$, I observed ...
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Dispersion relation in string vibration

In case of a continuous,bounded string we know, the dispersion relation is linear, i.e, the restoring force is directly proportional with the wave propagation vector. In other words, $$w=ck$$ Where $...
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2answers
299 views

What sound does a vibrating membrane produce?

Suppose I have a vibrating membrane vibrating along some function $u(x,y,t)$ where $t$ is time and $x$ and $y$ are variable indicating a point on the membrane. What sounds are produced by this ...
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2answers
355 views

Why does a longer string vibrate longer before the damping brings it to rest?

While performing string vibration experiments under the boundary condition that both ends are fixed, I observed that the damping of the wave is much larger when the size of the string is smaller and ...
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0answers
76 views

Has the asymptotic theory of eigenvalues of infinite matrixes already been applied to vibrations analysis?

My question is reffering to the masses/springs model of a material, like the one presented in this article http://www.laserpablo.com/baseball/Kagan/UnderstandingCOR-v2.pdf. If one treates a long ...
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210 views

String vibration for inhomogeneous string

In case of the vibration of a homogeneous string under the boundary conditions that the string is fixed at both its ends, using fourier analysis we can show how the amplitudes of successive ...
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1answer
384 views

How does “sgnl” work? [closed]

I visited many sites and did lots of Google search but I didn't get my answer. In this link I read the article about how Sgnl works. and here's some text: "Sgnl will generate vibration through its ...
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180 views

Water meniscus oscillation

What is the general technique for obtaining the differential equation for water meniscus oscillation inside a container? In case of the simplest mode, sloshing, we can find out the frequency without ...
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0answers
31 views

Question on derivation of equations for a viscously damped vibrating beam

I'm trying to work through and understand the derivation for the solution of a vibrating beam that also has viscous damping. I'm using the following book: Rao, Singiresu S. "Vibration of Continuous ...
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1answer
448 views

Tuning fork having 2 arms [duplicate]

Why there is 2 arms in the tuning fork? It can have 1 or more than 2 arms. If we think to create more resonance, then we can construct a tuning fork having many arms
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2answers
2k views

Compute the damping value for two masses in a harmonic oscillator

Consider that this is a simple mass spring damper system: $$ \ m \frac{d^{2}x}{dt} = F - b\frac{dx}{dt} - kx\ $$ What I allready know is the force $ F $ and the mass $ m $. Then I can find the ...
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2answers
2k views

Fourier series analysis of string vibration

In case of a plucked string,the amplitudes of successive frequencies fall by 1/n^2. In case of a string which is struck so that say at x=a only the string has a velocity,say v,initially,then the ...
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1answer
59 views

Movement through vibration

I have a circular container with a flange which sits inside a hole in a table which is mounted on vibration mounts and is vibrated by a linear vibrator. The container is a clearance fit in the hole, ...
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1answer
1k views

Why is the Direction of Particle Vibration Opposite to their Displacement?

I've seen this Diagram in a lot of my books.I dont understand why the Directions at different nodes are dissimilar (Same for Ant-nodes).What exactly does these vibrating Directions actually mean and ...
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1answer
166 views

Standard linear solid model - dashpot “short out” at $t=0$

My professor said that at $t=0$ the dashpot in standard linear solid is "short out". Why? I know that the force of dashpot is ($u$ is the dislplacement): $$F_{\eta}=\eta \space \frac{du}{dt}.$$
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2answers
386 views

Correct definition of an 'acoustic mode'?

I am reading 'The Oxford Solid State Basics' by S.H.Simon in which on page 92 defines an acoustic mode as: ... any mode that has linear dispersion as $k\rightarrow 0$. Whilst on page 94 he defines ...
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1answer
26 views

will a force with same frequency as natural frequency make system resonance (in multi-dof)?

assume we have a multi-dof system and a force is applied with same frequency as one of the natural frequencies. will this system be resonant in any circumstances? (system is undamped).
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1answer
2k views

What is the difference between a rigid diatomic molecule and non-rigid diatomic molecule?

I started a mock paper for one of my entrance exams with this fairly easy question. I rearranged the equation and got 5/2, knowing that a diatomic molecule has a Cv of 5/2, i concluded that the answer ...
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0answers
63 views

Vibrating string - presentation suggestions [closed]

I will present a faculty work on the "Vibrating String" in a discipline of Experimental Physics. I needed something that was "out of the box" for the completion of the work, to make a good impact, but ...
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211 views

How can electronic transitions in atoms contribute to the vibration of molecules?

In Raman spectroscopy, light is inelastically scattered from a sample and the shift in the scattered frequency (the Raman shift) is related to the vibrational modes of the sample. [...] and should ...
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1answer
1k views

Gravitational Waves could be just vibrations in space and not spacetime fabric

Disclaimer: I have this doubt due to lack of knowledge, please clear my doubt without closing it or keeping it on hold. my doubt could be silly but please clarify the doubt. So my knowledge of ...
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1answer
9k views

Converting acceleration (g) or(m/s^2) to velocity (mm/s) [closed]

I have a set of acceleration values taken from accelerometer given in 'g' or 'm/s^2'. I would like to convert it to velocity 'mm/s'. is there any formula to convert it? Note: I don't have time or ...
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2answers
2k views

What are the eigenfunctions and eigenvalues of a moebius strip? [closed]

A Moebius strip is a simple example of a non orientable surface. Suppose a very thin metal model of one, say of length $2\pi L$ (midline), width a, thickness negligible is perturbed ("kicked"), and ...
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1answer
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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 ...
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1answer
365 views

Help with formula for musical instrument [closed]

The formula is: $$ f = \frac{3.5161}{2\pi L^2}\sqrt{\frac{EI}{\rho A}} $$ $A$ = area, $\rho$ = density, $I$ = second moment of area cross section, $E$ = Young's modulus, and $L$ = length. Can anyone ...
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2answers
37 views

Frequency discrepancy: harmonically forced, Undamped, mass-spring system

I got an undamped mass-spring system: \begin{equation} {\frac { {d} ^{2}y}{ {d} t^{2}}}+4\pi^{2}y=0.0942*(0.0227 - 0.236*\sin(5.0631 - 2\pi*2t)) \end{equation} where $y$ is displacement. The two ...
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2answers
846 views

What is the difference between damping and elasticity forces?

From DYNAMICS OF STRUCTURES, Third edition, by Ray W. Clough and Joseph Penzien Damping has much less importance in controlling the maximum response of a structure to impulsive loads than for ...
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1answer
57 views

How to determine the linearity of a numerically simulated mass-spring system?

I did some numerical simulation of a mass-spring system, which is a 2D 1-degree-of-freedom spring-mounted cylinder vibrating due to moving fluid surrounding it. The cylinder's motion may be described ...
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238 views

Physical example for a non-linear mass-spring system?

Let's say there is a mass-spring system: ${\frac {\mathrm {d} ^{2}x}{\mathrm {d} t^{2}}}+2\zeta \omega _{0}{\frac {\mathrm {d} x}{\mathrm {d} t}}+\omega _{0}^{\,2}x=F$ I would like to ask for a real-...
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1answer
209 views

Is it a linear mass-spring system?

Please look at this equation representing a mass-spring system: ${\frac {\mathrm {d} ^{2}x}{\mathrm {d} t^{2}}}+2\zeta \omega _{0}{\frac {\mathrm {d} x}{\mathrm {d} t}}+\omega _{0}^{\,2}x=F$ where ...
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2answers
93 views

How to mathematically prove that a linear system's vibration frequency is equal to frequency of the harmonic external force?

I was reading about "Vibration" on Wikipedia: Forced vibration: 'for linear systems, the frequency of the steady-state vibration response resulting from the application of a periodic, harmonic ...
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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 ...
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0answers
156 views

Where do air molecules move at the greatest speed in a sound wave?

In my lecture notes it states that The movement of the particles is greatest were the gas is rarefied. But I wold disagree. I would think that the speed of particles is exactly zero at the ...
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1answer
760 views

Chladni Patterns [closed]

I'm trying to make a simulation for Chladni plates the diagram above shows the patterns on rectangular plates, and relates them to 2 values (n, m) many of the explanations suggest that (n) is the ...
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2answers
443 views

a Non-linear Mass-spring system with different force and vibration frequency?

I got a classic mass-spring system with zero damp ratio, having weird behaviour. The input frequency of external force is twice that of the output displacement results. While linear systems' input &...
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2answers
299 views

Vibrations - bouncing ball

I have a system with platform that has mass $m_1$ and ball with mass $m_2$, platform is connected to spring with some $k$ and damper $c$, with initial conditions of position and velocity of ball and ...
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1answer
137 views

Probability of two vibrating beams touching

Problem set-up I am looking at two adjacent elastic cantilever beams. They are micron/nanoscale size and so they vibrate due to thermal noise. The problem I am trying to solve is whether the ...
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1answer
529 views

Finding the effect of air resistance on period of oscilation without differential equation

I'm currently working on the "cavendish" experiment and wish to use/develop a method separate from the casus we've been provided. Now I've nicely calculated and derived everything I need to know, ...
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1answer
89 views

Do sounds waves created by human speech penetrate the body?

I'm not sure if this question is quite fitting. But does sound penetrate the body in a "usable" way? By that I mean if we were to somehow implant a small microphone inside the body (not too deep) ...
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1answer
619 views

sound travelling through a tube

I am an artist who is designing some interactive play equipment for a playground. One of the playground components is a talk tube feature. The child will speak into a flower sculpture, cone shaped ...
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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 ...
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2answers
1k views

Does the frequency of an object in vacuum remain constant

Suppose there is an object(say a pendulum) in vacuum. When a force of certain magnitude is applied on this object, it starts vibrating with a particular frequency and amplitude. Now if the magnitude ...
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2answers
82 views

What is the cause and meaning of harmonics?

Let's suppose that a cantilever is vibrating at a frequency of 2Hz. That means that it goes up and it comes down twice per second. I don't understand what the term harmonic means. I can't grasp how ...
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1answer
939 views

How many natural frequencies does a beam have?

If you take a real 3D beam, how many natural frequencies does it have? Likewise, how many natural frequencies does a beam have if it's a one dimensional, like an Euler beam?
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3answers
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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, ...
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2answers
730 views

Why isn't the resonance frequency of a vibration the damped frequency? [duplicate]

I had studied the damped forced vibration and had come to know that the angular speed of force which creates resonance is Which is counter-intuitive to me that the angular frequency should match ...
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2answers
289 views

Can EM Waves Cool Water Rather than Heating It?

In chemistry class recently, my teacher was telling us about how a microwave works. She says that the EM waves emitted by the microwave hit the water molecules in food and cause them to vibrate faster ...