# Tag Info

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There have been lots of experimental attempts to test the validity of Coulomb's $r^{-2}$ law. Many of these are reviewed by Tu & Luo (2004), and is where I am getting the numbers quoted below. Somewhat equivalently, experiments have looked at trying to set an upper limit to the photon mass, which is testing the hypothesis that rather than a $r^{-1}$ ...

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I am only going to leave a brief answer, seeing that the comments are very accurate. The paradox can simply be resolved by considering the elastic nature of all the objects. How so ever instantaneous might the $dt$ or the time of collision seem to the human eye, actually it occurs over a small duration, based on the elasticity of both the objects involved in ...

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Coulombs law as well as Amperes law and similar mathematical formulations of two centuries ago, were incorporated within the strict mathematical format of Maxwell's equations . The apparently disparate laws and phenomena of electricity and magnetism were integrated by James Clerk Maxwell, who published an early form of the equations, which modify ...

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We know from the fact that the wood block is floating that it is less dense than water. I will assume the coin is more dense than water. I will also assume that we are considering steady state after any waves have died away. I will also assume that the wooden block remains in the same orientation as before. I will also assume the block is cubiod. I will also ...

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Force is not divided, it applied to the first bag, and then the first bag will make a force on the second one, and the second on the third. The first bag feels two forces, the one you apply and the reaction from the second bag, the second bag in turns feels two forces, one from the front bag and one from the rear bag. If the bags are attached trough ropes, ...

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Physics is an observational science. It measures and observes the way nature behaves, and ever since Newton, models these measurements and observations with mathematics. Mathematics is a discipline where one starts with axioms uses logic and arrives to theorems and expressions that can be proven using the axioms and other theorems. One ends a proof in ...

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Acceleration due to gravity remains roughly constant near the surface of the earth. Yes, $a = F/M$, but as mass increases, the force exerted by gravity increases too($F\ \alpha \ m1m2\over r^2$), keeping $F/M$ or $a$ roughly constant around the surface of the earth

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Here's how to intuitively understand that $a=g$. Take a metal ball having mass 1kg and drop it. Its downward acceleration is $9.8m/s^2$, right? Now take a second ball and drop it. Same thing, right? Now drop both at the same time. Same? Now connect them together (with a tiny drop of weld metal) into a single 2kg mass, and drop them. Do they suddenly slow ...

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I might be erring something basic here, so downvotes are welcomed, but I would love if they include comments to correct this answer, or just erase it. I do not believe the Coulomb law has been tested beyond the order of a few meters. Arguing that light remains unchanged across the universe should be irrelevant. The reason is that the electrostatic and ...

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To see that your integral expression does not make any sense, imagine that $\vec{r}(t)=( x(t),y(t))$ describes a circle. Then the line integral of the force around the loop gives the change in potential energy, which should of course be zero, $$\oint \vec{\nabla} \phi \cdot \vec{dl} = \Delta \phi =0.$$ But if you insert the actual values from your ...

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I know of two reasons for why we should consider gravity to be a force. The first is purely classical and Newtonian: tidal forces. Gravity is solely responsible for producing tidal forces, and they cannot be considered a fictitious force, whereas the usual acceleration due to gravity in some sense can always be thought of as fictitious. The way you know ...

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you could do that by replacing gravity (that is ultra-weak) by another similar force (i.e. attraction in $\frac 1 {d^2}$ ), like electrostatic. It's easy to act on small charged objects. (but if you want a liquid to be attracted, it's more difficult :-) )

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If all of them feel the same force, they would have an acceleration that would give them a speed and hence a kinetic enegy greater than the work done by the applied force. It would violate the conservation of energy and conservation of linear momentum principles. The force on each bag will depend on their individual masses, you can compute the acceleration ...

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