Recent content by dgOnPhys

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    Centripetal force in a curved road

    You're right that's more likely what he was referring to: the OP thought was suggesting there would be another force acting on the tires to cause friction as in an equilibrium case Let's see if Shyan ever clarifies
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    Relationship between acceleration and distance

    Trying to make a comparison using data taken at the same velocity is somewhat involved. It is a lot easier to plot distance versus time and compare the graphs (see attachment). As you can see the RS4 is consistently ahead of the EVO even if their accelerations compare differently along the...
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    Centripetal force in a curved road

    I guess by "another force" you meant the opposite force that has to exist because of Newton's 3rd law; this is not causing the centripetal force though, forces simply exist in pairs. In any case this force is the force the tires exert on the road (in an inertial frame) and it is obviously not...
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    Uniform radial electric field?

    It is easier to see what's going on by calculating q(r) for r<R, this goes as r^2; the problem is really that density in a radial variable is not such an intuitive quantity
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    The divergence of 1/r^2 fields

    This is somewhat correct: 1) the divergence of \vec A = A\frac {\hat r}{r^2} is zero NEARLY everywhere and the 'nearly' is very important because the integral of this divergence over a volume including the origin is not zero. Using distribution theory you would write div( A\frac {\hat...
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    Definition of electrostatic potential difference

    Hi Neel it is fairly simple to see what happens in the specific case of two generic point charges. Place the reference in the midpoint with both charges on the x-axis (say a and -a are the abscissae of the charges). Consider the path going from one charge to the other along the x-axis. The...
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    Are Fictituous Forces Conservative?

    Hi tiny-tim, I am not really following your line of reasoning: - Euler force cannot be expressed as a gradient (F.ds is not a closed differential form) so it cannot be conservative. Even in the simple OP case, the CM frame rotating with the masses will experience angular acceleration (e.g...
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    Power Expantion in Lagrangian Derivation

    Hi tharchin, I don't have the book at hand but he is probably just talking of a Taylor expansion of the integrand L(q+\delta q, \dot q + \delta \dot q, t ) = L(q, \dot q, t ) + \frac{\partial L}{\partial q}\delta q +\frac{\partial L}{\partial \dot q}\delta \dot q
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    Are Fictituous Forces Conservative?

    Hello vodka, interesting question, from what I gathered I would say that only the centrifugal force is strictly conservative (can be expressed as a gradient), neither Coriolis nor Euler fictitious forces appear to be conservative: the first depends on velocity, the second does not create a...
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    Solving ODE with Data Points: Finding Equation and Integrating Method

    Otherwise if you are daring you can try wolframalpha.com [integrate 1/(a*x^b - c*x^d)]. Spoiler: you'll have to like the hypergeometric function
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    Magnetic or Electric Field or Electromagnetic Field?

    I think this is a second order effect we are looking at the low velocity limit (first order approximation) here, right?
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    Creating Sparks Through Air - Adrian's Physics Experiment

    If you want to get high voltage w/o too much work you can try an ionizer, these days you find them a bit everywhere, e.g. air filters, hair driers. Just make sure you know what you are doing before messing around with them. If you want to go big and do not mind the work, van der Graaf is your...
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    Invariants of a characteristic polynomial

    I guess we are talking matrices in 3-dim and you are referring to the sum of the determinants of the diagonal minors of order 2. What do you mean by why? Isn't it enough that they are coefficient of the characteristic polynomial? You can also specifically prove to yourself that this quantity...
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    Conservation of Momentum and Energy of metal pucks

    Interesting result, I guess in the second case you can still get electromagnetic field to carry away energy and momentum but I doubt that can account for that much. A more likely contributor could be Eddy currents in conductors, were the puck conductive or moving over a conductive surface?
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    How Does Dirac Challenge Classical Mechanics Assumptions in Quantum Theory?

    More simply a non-holonomic costraint is any constraint that cannot be reduced (e.g. by integration) to an holonomic one; in general it will be a function of coordinates, momenta and time.
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