Questions tagged [vibrations]
The vibrations tag has no usage guidance.
474
questions
2
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1answer
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Why do wet papers create no sound at all?
When we tear a dry paper, it produces a clear audible sound but when the same experiment is tried with a wet paper, we hardly hear any sound.
So can someone explain me what is happening here at the ...
1
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1answer
37 views
What is modal analysis?
I know what modal analysis is, and I know how to conduct one. I can get the eigenvalues and vectors (modes). Not a problem.
However, I am lost at trying to understand the philosophy of what it is.
By ...
1
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2answers
38 views
Finding the Full width half maximum of a function
I am a bit confused as to how we calculate Full-Width-Half-maxiumums (FWHM) of a function.
Consider a function as $$f(x) = {\frac{\sin(ax/2)^2}{(ax/2)^2}} \cos(bx/2)^2 $$
where b>>a.
It looks ...
0
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1answer
42 views
Can a particle transcribing motion described as $y=(\sin x)^2$ be called to be in vibration? [closed]
I know that $\sin x$ or $\cos x$ curves can be said to be "in vibration," but what about $(\sin x)^2$?
1
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1answer
22 views
How to analytically derive the equation of the amplitude of the force being transmitted to the ground of a damped, forced vibration system
For this question, I really have tried to produce some working but the entire thing is just deeply confusing me.
I know my equations for the displacement of this mass will be as follows:
I have ...
0
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1answer
44 views
Is pulling and pushing the same?
In the following image, you are asked to create an equation that represents the position of the moving part as the magnet pulls the metal object.
If the force acting on the system is constant and the ...
0
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0answers
40 views
Harmonal density Probability changes?
I have been thinking about strings vibrating. we usually see a purely elastic string in modes of vibration as states of modes. I was thinking, what if we changed the length of the string dL such that ...
0
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1answer
36 views
Frequency of spring and pulley system [closed]
I need some help with this problem.
I have to find the natural frequency of this system, the problem says that the cylinder has a mass of $m$, spring constant is $k$ and the string to the right is ...
2
votes
1answer
53 views
Materials that behave as “metals” for sound waves?
Probably the most well known property of metals are that they are shiny. Ultimately arising from the high density of conduction electrons capable of carrying current, this shinyness is means that ...
1
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1answer
14 views
Why the frequency of sound can vibrate the object if the frequency of both is the same (resonance)?
I mean what actually happens so that sound can vibrate an object? If both frequencies are subjected to constructive interference then resonance, why doesn't the sound only increase in amplitude rather ...
0
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2answers
42 views
Motion of molecules is random or uniform vibration with a frequency?
Every substance has an entropy, entropy is defined as the randomness in a system. There's also a term called molecular vibration which tells the periodic vibration of molecules and gives them a ...
2
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3answers
68 views
Why is the vibrational kinetic energy of a body ignored when calculating the total kinetic energy?
In calculating the total kinetic energy of a macroscopic rigid body, we add the total translational kinetic energy and the total rotational kinetic energy of the constituent particles. Why is the ...
1
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2answers
124 views
Defying gravity with vertical shaking? [closed]
I saw this video on levitating a denser liquid on less dense air by vertical shaking. But I couldn't understand some points in the video. Particularly:
How did the liquid levitate?
I think it's ...
0
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2answers
40 views
Intuition behind forced oscillations
in every book I own and on the internet, any information on forced oscillations is a version of the following definition, followed by the solution to a differential equation.
Forced oscillations: ...
0
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2answers
63 views
Heating water manually
Is it possible to heat a small amount of water, may be a cup of it, only by human force, using a small scale version of a device like Joule used to prove the heat mechanical equivalence, just by inner ...
-2
votes
1answer
37 views
Reverse deadblow hammer? [closed]
Exploring the benefits of deadblow hammer physics in sports.
I play badminton, and have developed elbow pain that is aggravated whenever I smash (overhead forehand, like a tennis serve). This is ...
0
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0answers
27 views
How does time translational invariance and linearity imply exponential solutions?
I'm currently studying "Waves and Oscillation". While going through the book The Physics of waves, from page 11-12. The author has mentioned that the differential equation being linear ...
0
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1answer
36 views
Resonance and standing waves on a bar [closed]
I'm having trouble solving this problem:
By applying a harmonic force, acting on the end of a free bar of length $L$, a standing wave is formed due to multiple reflections:
Where are the nodes of ...
2
votes
1answer
59 views
Derive shape of sound wave from vibrating string simulation
I have a physical simulation of a vibrating string (made with matter.js). From this, how can I derive the sound wave / air pressure over time, that would result from such a string?
I had considered ...
0
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0answers
8 views
How to calculate strouhal number/vortex shedding frequency of the airfoil using mathematical approach?
As a part of my thesis, I am trying to find when the airfoil starts to flutter by changing pitch angles. I've computed the results in ANSYS Fluent. But now I've to calculate the same using a ...
2
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0answers
188 views
Deriving a model of a point-driven Chladni plate
Please note ā this question considers a point-driven Chladni plate, not Chladni's classical experiment. I'm aware of various other questions concerning the latter here on Physics.SE.
As the title ...
-3
votes
1answer
51 views
Because of the spacetime foam, we can't calculate a complete string, we can only calculate parts or ends, right? [closed]
What is the relationship between the vibration of the string and the uncertainty of space-time.Not seeing the string, but when doing calculations, some parts of the string are affected by spacetime ...
0
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1answer
39 views
How do you determine energy transferred to a trampoline when a ball is dropped on it? [closed]
Suppose a ball of mass $m$ is dropped over a trampoline(consider the young's modulus of the material to be $Y$) from some height $h$. The ball impacts the trampoline, gets slowed down due to the ...
0
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1answer
21 views
Generalized force expression for this “airplane” oscillator system?
I am reading a book on aircraft dynamics (Blakelock Aircraft and Missiles) where the author presents the following system on page 408:
Lagrange's equation is given by:
$$
\frac{d}{dt}\left(\frac{\...
37
votes
3answers
3k views
Why does glass, in spite of being amorphous, often break along very smooth surfaces?
When a crystalline material breaks, it often does so along planes in its crystalline structure. As such this is a result of its microscopic structure.
When glass breaks however, the shapes along which ...
0
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1answer
29 views
Difference between vibration and oscillation considering a point in space
Most answers and articles I've read so far try to give real world examples such as a spring or a pendulum. However, I'm trying to understand the core difference between the two terms in the most ...
0
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0answers
36 views
Do solids heat up on compression or extension? If so how?
Well, let's take the example of a compressible solid. We know that in order to compress a solid we need to apply a force "greater(and not really equal)" than the interatomic/intermolecular ...
0
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2answers
46 views
How can I measure the frequency of vibration of a surface/object?
I'd like to know if there is a solution that allows me to measure the frequency of vibration of a surface/object. Primarily I am seeking to improve my speaker/home audio setup. The vibrometers I've ...
1
vote
1answer
28 views
How does contact area affect the transmission of vibration from one object to another? [closed]
I'm studying sound, and speaker isolation solutions specifically. I keep seeing the idea that spikes reduce the transmission of vibration due to the small contact area, but couldn't find any material ...
1
vote
4answers
89 views
Plucked string at $t=0$ and its Fourier decomposition
Decomposing a function into a Fourier series is possible for periodic functions. Fourier transform, on the other hand, is used for aperiodic functions. How can we use Fourier series to analyse the ...
0
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0answers
23 views
Recommendations for good books on mechanical vibrations
I'm looking for books that explain/model vibration concepts such as multi degree of freedom vibrations from a mechanical vibrations standpoint (not waves). I'd prefer if it has proofs for most ...
0
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0answers
46 views
Equation of Motion for a Structure Vibrating near the Speed of Light
For a standard $N$ DOF system we can find the eigenfrequencies and eigenmodes of the system by setting up an eigenvalue problem in the form of
$$
([M]-\omega^{2}[K])\phi=0.
$$
For a continuous ...
1
vote
2answers
97 views
Solving a differential equation [closed]
($x$ here refers to position)
$\frac{d^{2} x}{dt^{2}} + Ļ^{2}x$ = 0
After solving the above differential equation, we get
$x(t) = Ae^{iĻt} + Be^{āiĻt}$ where $A$ and $B$ are some constants.
My ...
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0answers
18 views
More formal definition of admissible functions and expressions of $T_{m}$ and $V_{m}$ with the Rayleigh-Ritz Method
In this textbook I'm reading on the Rayleigh-Ritz method, they define an admissible function (in the context of finding natural frequencies and modes of vibrating beams) as a function which doesn't ...
1
vote
1answer
37 views
How does sound get generated when you whistle?
how does sound get generated when you whistle?
I.e. what creates the sound/vibrations when you whistle on your lips?
2
votes
2answers
174 views
Questions on asymmetric nature of mass and stiffness matrices
EDIT: I now know the answer to my second question after re-reading relevant parts of my textbook and reading Eli's answer.
I was under the impression that mass and stiffness matrices are always ...
0
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1answer
57 views
Physical meaning of Damped Exponential Sinusoidal [closed]
$$x(t)=A\sin(tf+p)e^{-dt}$$
The equation is used for damped exponential sinusoidal, if used for stress decomposition does it have any physical value, especially the exponential $d$?
2
votes
3answers
100 views
What makes a transverse wave maintain its shape?
Consider a simple transverse wave propagating along a rope. We understand it's propagation stating that each point is pulled by its neighbors, making it act along with them. This will create a similar ...
0
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2answers
31 views
Does resonance by sound waves, or by any other similar means, occur at the molecular level?
When the frequency of sound waves match the resonant frequency of a structure, like a building or a window, resonance occurs which is clearly visible. This frequency depends upon the material and it's ...
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0answers
10 views
Is it possible to probe the molecular vibration of diatomic molecules without a dipole moment by some way?
I was reading about the vibration frequencies of molecules, and I realised molecules like iodine (diatomic) have only 1 vibrational mode, and the vibrations are too weak to be probed. Is it possible ...
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0answers
30 views
Floating foam organized in circles
I was walking by the kitchen when I saw the bowl in which my mom had put some beans in water to soak before cooking them. The thing is that I saw these concentric circles made out of the foam/bubbles ...
0
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0answers
16 views
Effect of initial shift on undamped forced oscillation
I have general equation for undamped forced oscillations (no friction) which is:
$$x(t)\ =\ \frac{v_0}{\omega_n}\cdot \text {sin}\left( \omega_n \cdot t \right)+\left(x_0\ -\ \frac {f_0}{\omega_n^2-...
0
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0answers
36 views
How does the resonant frequency of a glass slab depend on its thickness
I am interested in finding out how does the thickness of a glass slab change the resonant frequency of it. Since i know that resonant frequency not only depends on the material but also on the ...
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0answers
18 views
Solving single degree of freedom vibration system with opposing springs and dampers
I'm re-posting this as I put in the Maths Stack first but it might be better placed here.
As part of some analysis of data from a test rig at work, I thought I would have a go at solving the ...
0
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2answers
44 views
How does sound imparts vibrations to molecules in solids
How does sound imparts vibrations to molecules in solids which are tightly bounded. I understand the molecular bounding is very strong that is why it is solid and tough.
So how does mere a tap on a ...
2
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3answers
102 views
When a tuning fork is struck, how does the struck tine induce vibrations in the secondary tine?
Background
I'm currently writing a book on music theory and I'd like to include some background information on the physics of sound waves. My example of choice is to explain compression and ...
3
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0answers
34 views
Kinetic energy distribution by mass in mass-spring harmonic oscillator system
Basically I want to find a minimum working example of a non dissipative system that is able to concentrate kinetic energy on some subparts of the system.
My first guess was to use the coupled ...
0
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1answer
44 views
Cause molecular vibration without adding heat into the substance containing the molecules?
I know when a substance is heated the molecules in the substance begins to vibrate in random motion.
What I want to know is, is it possible to vibrate the molecules without adding heat to the ...
10
votes
1answer
521 views
Why does a book leaned up against a wall sometimes fall over after being stable for many hours?
This problem has been vexing me for years.
Sometimes, you lean a book up against a wall and it stays there (the static frictional force balancing gravity, etc), but then after a long time (hours or ...
3
votes
1answer
118 views
Electronic-vibrational-rotational Transition
I'm trying to simulate the fluorescent spectrum for the first time and run into several problems. The dipole matrix element for a transition between 2 different electronic states is as follow:
$$\...
