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1answer
9 views

The spring of air: Why does a piston undergo SHM when it is displaced lengthening the air-column inside a cylinder filled with air?

Let there be a cylindrical tube, closed at one-end, with a well-fitting but freely moving piston of mass $m$. [. . .] The piston has certain equilibrium position. If the piston is moved a distance ...
0
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1answer
33 views

A question about Undamped Vibration [on hold]

A small collar of mass 1-kg is rigidly attached to a 3-kg uniform rod length L = 1 m. Determine the period of small oscillations of the rod when (a) d = 1 m, (b) d = 0.7 m.
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1answer
69 views
+50

Finding the frequency of vibration of part of a system

The setup: 4 spheres of diameter $d$ are suspended on a horizontal plane (magically). They are arranged in a square with length $l$ (the vertices are correspondent to the sphere's centers). The ...
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3answers
35 views

How does any vibrating object generate sound?

We all know that vibration is the cause of sound generation. But here my question is, Internally what happens in vibrating object which creates sound? I guess, generation of sound will be some where ...
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2answers
139 views

How to use an accelerometer to correctly quantify the magnitude of vibrations

Consider the following setup: An accelerometer is placed inside a helicopter, measuring $g$ values along three axes $(x,y,z)$ every $10~\text{ms}$ (100 times a second), during a helicopter flight. ...
0
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1answer
14 views

Amplitude Modulation in dispersive mediums

I'm reading the book "Physics of Waves" by Georgi. In section 10.2 he says that to send a signal through one-dimensional dispersive mediums where the dispersion relation is not $\omega(k)=vk$ ($v$ the ...
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2answers
38 views

Is molecular vibration just phonon modes for a single molecule?

I'm reading about Raman Scattering, of which a big part is measuring the energy lost to/gained from Molecular Vibrations. I wasn't totally clear on exactly what is "vibrating" in vibrational modes (is ...
0
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1answer
29 views

Definition of mechanical impedance

Mechanical impedance is in the simplest (yet common) case defined as: $$ Z_m = \frac{F}{v} $$ where $F$ is force (let's assume 1D case) and $v$ velocity of the object (let's assume point of mass). ...
4
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1answer
235 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} = ...
8
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1answer
319 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 ...
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2answers
30 views

Vibrating Objects Part 2

Since I have an answer to Vibrating Objects, I am asking a part two about much faster vibration. What about vibrating an object at 1 THz or higher? What methods can be used? How much energy is spent.
2
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1answer
608 views

Spring system - 3 DoF system and its properties while changing stiffness

I was given the attached 3 degree of freedom spring system with the purpose of analyzing it. I came up with the following equation of motion and then I ran Matlab to calculate the corresponding ...
0
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1answer
30 views

Energy dissipation in damped oscillator (not driven by any external force)

If I have a damped oscillator (with no driving force), the energy of the oscillator will decrease like: $$E(t)=E_0e^{-\gamma t},$$ where $E_0$ is some initial energy and $\gamma\in\mathbb R^ +$. We ...
2
votes
1answer
49 views

Vibrating Objects

I'm not sure if this belongs in Engineering, but if it does, please migrate the question. What methods are used to vibrate objects extremely quickly? What are the most common?
1
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1answer
113 views

A moving brush on a vibrating surface

Hi group, I am a HS student in China preparing for a regional Young Physicist Tournament even. We are very puzzled about why would there be such movement. We would be grateful to see any inspiring ...
1
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1answer
69 views

What is the physical origin of acoustic modes in a duct?

Lets deal with wave propagation in a cylindrical duct. We ask the question: "what is the general form of a pressure wave which can propagate through the duct?" In answering this, we assume that the ...
9
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3answers
969 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 ...
0
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1answer
52 views

Simple pendulum cartesian coordinates

I'm reading Vibrations and Waves from French. I don't understand the following approximation when considering the simple pendulum: Referring to the last figure if the angle $\theta$ is small we ...
2
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0answers
27 views

What is the effect of vibrations on an object's properties?

What do vibrations do to an object's properties? By making an object vibrate at a high frequency (compared to its static state) would vibrations: Increase or reduce its moment of inertia? Increase ...
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3answers
2k views

Young's Modulus and Vibrating String Harmonics

I was wondering how Young's Modulus effects the resonant harmonics of a vibrating (string instrument) string. I know that the string's fundamental frequency is $$\frac{1}2 \times \text{Length} \times ...
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0answers
38 views

Effect on Q factor and resonant frequency when scaling down a damped oscillator to micro / nano scales

I've always just accepted that as you scale down a mechanical system the frequency and Q factor both increase. But how exactly do they scale? Linearly? With the square of reduction in size? Or maybe ...
8
votes
2answers
317 views

Why isn't in counting the no. of degrees of freedom, rotation about the axis running down the length of the molecule counted?

I was reading about the Equipartition Theorem. Then I got the following quotations from my books: A diatomic molecule like oxygen can rotate about two different axes. But rotation about the axis ...
4
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3answers
118 views

What is the relationship between vibration of the field and quantum fluctuation?

Consider a free field like the KG equation. I see that why $$\tilde \phi(\mathbf{p},t)$$ a momentum-dependent quantity, is an oscillator, vibrating at a frequency because when we apply the Fourier ...
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2answers
1k views

Can a simple pendulum be considered a simple harmonic oscillator?

Is the motion of a simple pendulum, a simple harmonic motion? It stops vibrating after sometime.
1
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1answer
77 views

How to reduce vibration on aluminum quadcopter? [closed]

I have an aluminum quadcopter with that's made of thin aluminum and its really flimsy. And there is lot of vibration when I fly it. My question is, if I make the frame stiffer so it doesn't bend, will ...
1
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0answers
26 views

Non-linearity of a guitar pickup

I basically understand induction and why a pickup generates a signal. (From: http://www.brighthubengineering.com/consumer-appliances-electronics/64277-the-physics-behind-the-electric-guitar/) What ...
1
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1answer
51 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 ...
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0answers
87 views

Modelling an Inelastic Collision

I've attempted to model the inelastic collision between a moving mass and a large stationary object, e.g. dropping an ball on the floor, for analysing the approximate kinematics and heat dissipation ...
0
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0answers
123 views

What affects the period and the frequency of a longitudinal vibration?

In a lab experiment, our objective is to observe the characteristics of longitudinal waves/vibrations. If we changed the mass and amplitude, I feel that they either affect the period and frequency of ...
2
votes
2answers
110 views

Coupled ODEs that model a quad rotor

I am working on modeling the vibrations of a quad rotor. The arms that support the rotors are fixed to a center plate; that is, it is pretty much a cantilever beam with an end load. Since this is the ...
1
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1answer
47 views

Air Presure and Air Velocity from speaker

How do I determine/calculate the air pressure emitted from a speaker ? And how to determine the velocity of air from the sound air pressure ?
1
vote
2answers
102 views

What is the meaning of pre-tension for a stiff membrane?

On one hand, I know that the tighter a drum head is stretched, the higher its natural frequencies. This relation is given by: $$f_{ij}=\frac{k_{ij}}{2\pi R}\sqrt{\frac{T_0}{h\rho}}$$ where $k_{ij}$ ...
0
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1answer
65 views

When an aircraft flies over, glass window vibrates…Infrasound?

When an aircraft flies over, my big glass window vibrates, making a ticktack beating. Its frequency sounds low, less than 10 beats per second actually. I'm wondering about the mechanism of this ...
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0answers
30 views

Isolate an electronic drum from the ground

Please note that I know nothing about this part of physics, so sorry if I make some mistakes. Drum is an awesome instrument, yet it can easily make your neighbours very angry.The vibrations caused by ...
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3answers
79 views

How does ultrasonic horn produce a convection current in the water?

When I was using ultrasonic horn in a beaker, I notice that there are convection currents in the beaker and stir up my substance. I don't understand why it produce water current, I thought that it ...
0
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0answers
22 views

Vibrational modes of a plate

What is the distinction between thickness-extensional, contour-mode/Lamb wave, in-plane shear, and the flexural modes of a plate, and under which conditions are each mode excited? Pictures for ...
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1answer
86 views

Is there always motion, when force is present? Is all motion vibration?

Even when you are seated in a chair, the chair is pushing up on you and you down on the chair (manifesting in the form of ~650N). While there is no obvious observable motion, is it not possible that ...
0
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1answer
174 views

Why does the pitch of a container being filled with water increase? [duplicate]

I wonder about this. If you pour water in a closed tank, it makes a noise. I have noticed that as the container becomes more and more full, the pitch of this noise also increases. Why is that? I do ...
1
vote
1answer
36 views

What does degrees of freedom mean in the context of vibrations?

If you have an $N$ degrees of freedom system what does this mean? What is the difference between a 1 and a 2 degrees of freedom system?
1
vote
1answer
45 views

Vibrationing molecules/atoms and the effect

If the molecules/atoms of a solid object vibrate quickly enough, would the way a human eye perceives that object be changed? Would the object appear to "flicker" or have almost a transparent look to ...
0
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0answers
28 views

What equation can be used to solve an ideal string/membrane in a non-vacuum medium?

I'm interested in the eigenmodes of the membrane for various mediums, such as vacuum, air, water, etc., which impose a damping effect on the membrane. This cannot be done by merely changing the value ...
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0answers
20 views

Can an axisymmetric solution produce antisymmetric eigenfunctions?

I'm solving a vibrating membrane. In order to simplify my calculations, it's tempting to assume axisymmetric behaviour. If I solve an axisymmetric problem, am I going to lose all the antisymmetric ...
0
votes
1answer
44 views

Meaning of ideal membrane

I'm studying from a mathematical point of view the bidimensional vibrating membrane. How can I define an ideal membrane? What are the assumptions when I say 'ideal'? Thanks!
0
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2answers
72 views

Finding the one-dimensional wave equation the vibrating string

It's a relatively simple problem and I've been able to solve it in a different way before, but the current book I'm learning from left me with some questions: After a few idealizations we get the ...
3
votes
1answer
83 views

Moments of vibrating string

I have to calculate first 10 moments for vibrating string with damping, but I don't know how to do it. I read about moments and in definition they mention linear system $$x'=Ax+Bu, \qquad y=Cx$$ with ...
0
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0answers
21 views

Calculate pressure distribution at plate surface

Currently I am having troubles calculating the pressure distribution $p(x,y)$ at the surface of a vibrating plate. I have a simply supported rectangular baffled plate which gets excited by a harmonic ...
0
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0answers
18 views

Transfer function of vibrating string [duplicate]

I need to find moments of vibrating string and I think that transfer function could be useful for this, but I don't know transfer function of vibrating string. Can someone give me some idea how to ...
1
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0answers
143 views

Calculate surface pressure due to forced vibrating plate using wavenumber space [closed]

My problem lies in the field of acoustics. I have a given complex velocity distribution. The velocity is the velocity in the normal direction to a rectengular simply supported vibrating plate. I now ...
3
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2answers
1k views

“Magic” Speed to Drive Over a Speed Bump: Myth or Reality?

A somewhat controversial aspect of speed bumps (sleeping policemen for those in the UK) is that they arguably cause more loss of life than they prevent by acting as a hindrance to emergency response ...
4
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2answers
454 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 ?