How Toppling shifts from one edge to other in a polygon shaped body, without any external force applied
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by Raja
2d ago
Please explain it to me that how the Toppling in a polygon shaped body shifts from one edge to the next adjacent edge while the object is already in motion, but without any sliding and no external force is applied. The confusion on my part is that the face which is about to fall against the floor surface does not rebound { like a 1-D rod does on collision after experiencing a impulsive force ( Normal reaction in that case ) }. Still explain the shifting of Toppling from A to Z ..read more
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What is the difference between a vector and a representation of a vector?
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by GedankenExperimentalist
2d ago
What does the phrase The wave function is a representation of the abstract quantum state. Or more generally, A is a representation of a vector $\vec V $ mean? What is the difference between a vector and a representation of a vector ..read more
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Boundary conditions for the stagnation point axisymmetric boundary layer equations
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by Domenico Lanza
2d ago
Good morning, I am trying to solve the Boundary Layer equations in the stagnation point in order to compute the stagnation point heat flux. In particular, the fluid is: -A continuum -In thermal and chemical equilibrium -Steady flow -The flow outside the boundary layer is inviscid, and there are no heat transfers -The only heat transfer is inside the boundary layer, on the stagnation point of an axisymmetric body, following the Fourier law: $\vec{q}=-\lambda_{eq} \nabla{T}$ -I am considering only the stagnation streamline, which is isentropic outside the boundary layer for the hypotheses made ..read more
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How to calculate a decent estimate for thermal energy flow rate in (or out) of a stationary car?
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by BadAtEngineering
2d ago
How on earth can I begin to calculate how the walls of a stationary, inactive car transfer heat? I am looking to do calculations for two states: one for a day in which the air is hot (let's say 95 degress fahrenheit) and with direct sun overhead, and one in which it is cold outside (let's say 30 degrees fahrenheit) with no sun overhead. Calculating the radiation give to the walls of the vehicle should be easy, in the sunny case. And calculating the thermal energy transfer in both cases through the glass should also be easy, as the glass is going to be a uniform thickness which is easy to measu ..read more
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Hamiltonian function
Physics Stack Exchange Forums
by Samir Rasulov
2d ago
I have some difficulties to understand the certain part here. The part which is shown with lambda_p * velocity and lambda_v * control input is not clear for me. As we already have constraints for velocity and control input, I do not understand the main concept behind these two terms. They have been shown as co-state components, but they are still unclear for me. Note: It is from the academic article named "Conditions to Provable System-Wide Optimal Coordination of Connected and Automated Vehicles". Thank you very much in advance ..read more
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Why is probability outside the infinite square well zero?
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by GedankenExperimentalist
2d ago
In an infinite square well, potential energy is given below, why is the probability of finding a particle in the position of infinite potential energy zero? $$V(x)=\begin{cases} 0,& \text{if } x \ \text{in}\ (-a,a) \\ \infty, & \text{otherwise} \end{cases}$$ The usual explanation is that because at the boundaries, $-a$ and a, the change in potential energy is infinite, making the force as well, causing the particle to stay in the well. But this explanation seems very classical to me (I mean we are explicitly talking about force on a particle which, I believe has no basis in quantum mec ..read more
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If we know forces and torques applied to one point of a rigid body, how do we calculate them for another point of a rigid body
Physics Stack Exchange Forums
by Heavenly T
2d ago
Suppose we have a rigid body with known length r that is fixed at point A. We also have a force-torque sensor at point A. The body is fixed such that it doesn't move. We apply forces to point B and get the values from sensor at point A. How can we translate the f-t values at A to f-t values at B? Are forces at A and B equal? If the body is in the equilibrium and we apply some unknown force F (0, x, 0, 0, 0, 0) perpendicularly to point B, get some non zero values Fy and Tx from sensor, will our x be equal to Fy ..read more
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Robustness to noise of a parametric oscillator
Physics Stack Exchange Forums
by Some random physicist
2d ago
I'm an experimentalist working with trapped nanoparticles with optical dipole trap experiments. In the experiment, surprisingly I observed that if I periodically modulate (at full depth) the trap intensity at a frequency much larger than the radial trap frequency of the particle, then surprisingly, I can see an extended dark lifetime (no photon scattering) of the particle in the trap (asymptotically approaching the vacuum lifetime) compared with the lifetime where I leave the particle in the static trap. My intuition for why this happens is related to the nonlinearity of the dipole trap but do ..read more
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Why are physicists not more concerned that there are too many explanations for redshift in the universe?
Physics Stack Exchange Forums
by John Hobson
2d ago
There are speculative explanations for red shift such as the tired light theory, but I am not referring to those. There are three mainstream explanations Red shift due the expansion of the universe giving rise to a Doppler effect. Cosmological red shift. The red shift is due to the stretching of light as the universe expands. Numerically, this seems to explain all of red shift, leaving no room for the other explanations. Gravitational time dilation. Time runs slower as the force of gravity, or the gravitational field, gets stronger. Slower time equates to a reduced frequency, which is a ..read more
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Derivation of the geodesic equation. Why do we start with the special relativistic action?
Physics Stack Exchange Forums
by Giovanni Brown
2d ago
I'm working on a derivation of the geodesic equation from the action functional. In special relativity, specifically for flat spacetime, we assume that the metric tensor is constant (not necessarily that it's not a function of the coordinates, but that it traces out constant distances between any two points in space since the metric is what keeps track of distances in geometry; maybe saying "it's constant" is wrong in this case). Anyhow, the lorentz invariant action for spacetime interval $ds^2 = g_{\mu\nu}dx^{\mu}dx^{\nu}$, which is lorentz invariant, the action in flat spacetime is given by ..read more
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