John Rennie
Reputation
99/100 score
 Nov 25 comment How does light behave within a black hole's event horizon? @SirCumference-Pies: I've just updated my answer and gone into the gory details of how the river model works. Nov 25 comment Value of $\langle x | p \rangle$ Hi Tom. I've typseset what I think you're asking. If I've got this wrong it should be obvious how to modify the Latex to correct it or you could just roll back the edit. Nov 24 comment Existence of a solution for geodesic differential equations for a singular metric Why all the votes to close? The question has a perfectly good answer i.e. that a singular metric is unphysical. Nov 24 comment Total angular velocity (Kerr metric) I'm a little surprised to see votes to close as homework. I think an answer describing the basic principles of the calculation seems perfectly reasonable. Nov 24 comment How the infinite electric field of an electron goes through a slit? The electric field is not just a property of the electron, it's a property of the whole system i.e. the electrons and whatever dielectric material makes up the slit. So the electric field doesn't go through the slit. As the electron approaches the slit the geometry of the electron + slit material system changes and the geometry of the electric field changes accordingly. Nov 24 comment Finding Friction and Coefficient of Friction Force? Hi and welcome to the Physics SE! Please note that this is not a homework help site. Please see this Meta post on asking homework questions and this Meta post for "check my work" problems. Nov 24 comment Power statement is valid for MW Or KiloWatts? 60MW per hour could be the rate of change of power generation. If you started with the plant generating no power and it took an hour to get the power up to 60MW then the rate of change of power generation would be 60MW/Hr. Nov 23 comment What is the sum of the angles of a triangle on Earth orbit? @ScienceAndPhilosophy: there are very, very few simple analytic solutions in general relativity! Nov 23 comment Odd question on potential energy The particle is never at the position $(0, 0)$. The question is merely stating you can define the zero of $U$ to be at the position $(0, 0)$. Nov 23 comment Odd question on potential energy Hi and welcome to the Physics SE! Please note that this is not a homework help site. Please see this Meta post on asking homework questions and this Meta post for "check my work" problems. Nov 23 comment Is the CMB Cold spot growing or shrinking? Can you clarify what you want to know, and specifically what isn't already covered by the Wikipedia article. Nov 23 comment equation related to room temperature and air conditioner temperature and flow rate? I'm afraid this is too broad a question to be usefully answered here. Nov 23 comment Which is more mechanically efficient, a bicycle or a unicycle? Hi Laff. We expect answers here to give detailed explanations. Can you explain how to calculate the frictional losses of a bicycle and unicycle then show the losses in the unicycle are lower? Nov 22 comment Validity of naively computing the de Broglie wavelength of a macroscopic object @user929304: macroscopic objects do not behave like quantum objects so they do not have a de Broglie wavelength. This is because they decohere too fast. It is nothing to do with their momentum. Nov 22 comment Wavelength of light in a gravitational field Extremely massive stars (like O and B stars) are hot and blue not red. Extremely large stars tend to be red because they are usually red giants and quite cool. Nov 22 comment Measure ball's acceleration down inclined plane Hi and welcome to the Physics SE! Please note that this is not a homework help site. Please see this Meta post on asking homework questions and this Meta post for "check my work" problems. Nov 22 comment Why does heating eggs not change the State of matter from solid to liquid Hi toogley, the post I've linked ass exactly the same question as you do. Nov 22 comment Standing waves as plane waves Have a look at this article, section 13.5, page 13.3. This explains why the electric and magnetic components are out of phase in a standing wave. Nov 22 comment how is current measured through ammeter? Possible duplicate of Conversion of Moving coil galvanometer to ammeter Nov 22 comment Wave function collapse and Schrodinger's equation without measurement You might be interested to search for lots more on wavefunction collapse on this site.