# Tag Info

39

If there were only one prong (imagine holding a metal rod in your hand), then the oscillation energy of the prong would quickly be dissipated by its contact with your hand. On the other hand, a fork with two prongs oscillates in such a way that the point of contact with your hand does not move much due to the oscillation of the fork. This causes the ...

29

I am by no means an expert in tuning fork design, but here are some physical considerations: Different designs may have different "purities," but don't take this too far. It is certainly possible to tune to something not a pure tone; after all, orchestras usually tune to instruments, not tuning forks. Whatever mode(s) you want to excite, you don't want to ...

23

The reason for having two prongs is that they oscillate in antiphase. That is, instead of both moving to the left, then both moving to the right, and so on, they oscillate "in and out" - they move towards each other then move away from each other, then towards, etc. That means that the bit you hold doesn't vibrate at all, even though the prongs do. You ...

11

Q. How do two coupled vibrating prongs isolate a single frequency? howstuffworks.com has an article on How Tuning Forks Work The way a tuning fork's vibrations interact with the surrounding air is what causes sound to form. When a tuning fork's tines are moving away from one another, it pushes surrounding air molecules together, forming small, ...

6

It would depend on damping effects being taken into account or not. Invoking Newton's 2nd Law of motion, a differential equation for the motion of a damped harmonic oscillator can be written (including an external, sinusoidal driving force term): $m\frac{d^2x}{dt^2}+2m\xi\omega_0\frac{dx}{dt}+m\omega_0^2x=F_0\sin\left(\omega t\right)$ Where $m$ is the ...

5

The first generation of elementary particles are by observation not composite and therefore not seen to decay. They are shown in this table of the standard model of particle physics in column I. The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column and the Higgs boson in the fifth. All ...

4

Any physics-oriented FEM solver should do this. I have only done it with COMSOL, which is proprietary and expensive, but searching Ubuntu's repository of free software turns up at least two promising candidates: Elmer and FreeFEM. I'm trying out Elmer now. http://www.csc.fi/english/pages/elmer http://en.wikipedia.org/wiki/Elmer_FEM_solver This example ...

4

The major problem with ultrasound as a mechanism of purification is that it doesn't break molecules. Heat at least denatures proteins and breaks hydrogen bonds, but ultrasound is of a just smaller order of magnitude of energy at the atomic scale, which can be of the order of the adhesive forces holding the liquid together, but not of stronger molecular ...

4

The Moon moves away about four inches a year on Earth, 15 while the Earth's rotation is slowing down, which will in the distant future total solar eclipses occur stop the moon not having sufficient size to cover the solar disk. In theory, this separation should continue until the Moon takes 47 days to complete one orbit around our planet at which our planet ...

4

In an experiment in which particles are collided, a resonance is a large peak in a cross section (rate at which a process occurs) when plotted against the energy of the incoming particles. For example, when LEP collided electrons with positrons, they saw a resonance when the energy of the incoming particles equalled the mass of the $Z$-boson. Resonances ...

3

No, because in a vacuum, there is no way for the two tuning forks (I think you meant this, rather than pendulums) to communicate. The reason a second tuning fork with the same resonance frequency will begin resonating is because, physically, sound waves are hitting it at its natural frequency. Sound waves travel in a medium, so in a vacuum, there's nothing ...

3

The oscillator frequency $\omega$ says nothing about the actual oscillator phase. Let us suppose that your oscillator oscillates freely like this: $$x(t) = A_0\cdot\cos(\omega t + \phi_0),\; t<0.$$ At $t=0$ it has a phase $\phi_0$. Depending on its value the oscillator can be moving forward or backward with some velocity. If you switch your external force ...

3

There seem to be a lot of human body mechanical models, such as this one: As for applications, I have heard that sub-audio frequency vibrations have been considered as nonlethal weapons for riot control.

3

The inductor and capacitor form a resonant circuit, which will pass only a specific frequency - the one you are tuning the radio to recieve. You normally tune it by making either the inductor or capacitor adjustable. edit: As described in How does radio receives signal from particular station? it's very much like a pendulum. Current flows freely in the ...

3

Both "perfectly open" (zero acoustic impedance) and "perfectly closed" (infinite acoustic impedance) boundary conditions are only idealizations that never occur in practice. For the case of the human vocal tract, they aren't even very good approximations. The "bottom end" of the resonating cavity is not, in fact, the lungs, but the vocal folds (as Georg ...

3

The first resonant vibrational mode for a string clamped at both ends looks like: You should be able to deduce the wavelength from that diagram. The second mode looks like: Both of the images above are from http://www.clickandlearn.org/Physics/sph3u/Music/Music.htm and that site will spell it out in more detail for you. If your string length is ...

2

There's an interesting question in here if you look hard enough. First of all, there's nothing special about the resonant frequency of something made of little magnets. It might as well be a piece of ordinary string, a metal bar, or whatever. In fact I think the fact that it's made of separate little magnets stuck together would give it a much lower Q ...

2

If you have two decoupled oscillators, they satisfy differential equations $$-\frac{d^2}{dt^2}x_i=\omega^2_{i} x_i$$ where $i=1,2$. The solutions are clearly multiples of $\cos(\omega_i t+\phi_i)$. Now, consider two interacting oscillators. Each oscillator must know about the phase of the other, so the simplest dependence is to add a multiple of $x_2$ (a ...

2

OK, the simple answer: When there is a resonance in the antenna you have a coherent phenomenon. All the bands of electrons of the antenna are marching in tune. The black body radiation is an incoherent phenomenon coming from the individual atoms of the antenna. Even if the peak of the black body radiation were sitting on the resonance of the antenna it ...

2

The derivative-like line shape is a result of the use of field modulation. In order to get sufficient signal to noise, the B_0 field (large, static field) is modulated (usually at 100kHz) and a lock-in amplifier (or equivalent) is used to reject any frequencies beside 100kHz. The result of this field modulation is that the signal that is obtained is not ...

2

Real LC circuits have some resistance, which wastes some of the energy as thermal radiation, and the cycling eventually dies. I think they also have some other non-idealities that allow energy to escape as far field electromagnetic radiation, correct? What are these non-idealities? Are they independent of the resistive component? ...

2

This is a resonance in the circuit--- when you have a bunch of different frequencies driving a resonant system, the response is only strong for those frequencies which are close to the natural frequency of the resonant oscillator. You can see the same phenomenon in mechanical systems. If you have a mechanical mass on a spring, and you apply a force which ...

2

This must be impossible, even for lady Castafiore with her earthquake voice. For a glass to break by sheer sound you need to produce a tone equal to the glass's natural frequency - the frequency at which a body vibrates with the least amount of energy. In other words: there you get the most vibration with a minimum of effort. This is also called resonance. ...

2

The the car behaves like a musical instruments (e.g trumpet). If the turbulence reach the resonant frequency you hear the huge loud. Changing the size of the open part of the window you have to change the velocity of the car in order to hear the "explosion". It is like you are playing your car :)

2

In the quantum mechanical conceptual framework, the boundary between particles and (excited or ground) states vanishes. A particle is a state, and a state is a particle. (More precisely, particles are eigenstates of the operator of energy - in the low-energy case - or the operator of mass - in the high-energy case.) A physical system with a ladder of energy ...

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Simple: at higher speeds the kinetic energy of the air skimming the window increases, so the sound waves become larger in magnitude. The amount of air involved is proportional to the size of the window. The size of the window will also affect the pitch of the note, because the resonant frequency will change. http://en.wikipedia.org/wiki/Helmholtz_resonance ...

1

Vibrations begin to resonate together into sound waves we can hear. We can make the sounds loud or soft depending on how much pressure we place on finger. The pitch of the sound can also be changed by adjusting the amount of water in the glass.As you rub your finger on the rim, your finger first sticks to the glass and then slides. This stick and slide ...

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I'd be very surprised if a lump of sludge blocking a sewage pipe had any useful resonance. The idea of using a resonance is that the amplitude of oscillation builds up rapidly in response to the sound. However this will only happen if the oscillation has a high Q i.e. if it doesn't dissipate much energy. For a wine glass this is a good approximation, hence ...

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