Recent content by lowerlowerhk

For me, energy describes how quantities could trade with each other, eg to trade speed for distance, and the ratio of these trades are called conservation of energy. I tend not to imagine energy as something physical, but a mathematical construct to describe to ratio of how quantities are...

Good point, didn't notice that before. There is a historical reason of this swapping. For gravity, Newton's Law of Gravitation is well known before formulating gravitational Gauss's law, so the G is left as it is by convention. For the Electrostatics, the reason to add a 4pi to Coulomb's law is...

To add another perspective: It depends on where do you start deriving the equation. If you adding a constant to inverse square law of gravitational force, then there is no 4pi; If you start by treating gravity as charges distributed in a sphere and apply Gauss's law, there is a 4pi.

Break down the velocity vector of the solid body into two components: one is tangential to the sphere, another one points to the centre of the sphere. Reverse the direction of the central component and add the two component together and you will have the bounce off velocity vector. The angle...

I got an answer, not sure if it is the complete answer: The reason to not define time as another vector is that, in classical mechanics, the value of time is independent of reference frame. In math terms, it means that the value of time does not change under a coordinate transform and thus the...

Let's see if I think correctly first: I think a vector is a group of numbers independent of each other. What we say 3D vector means "it takes three numbers to specify a position and these numbers are not (explicitly) dependent on each other. The so called 'direction' of a vector is a...

If relative simultaneity implies that one event that could be already measured w.r.t. one reference frame not yet measured w.r.t. another reference frame: then could one find an reference frame at which none of the events were measured? If such reference frame exists, could one observe the...

Our Earth is going to be engulfed by the sun eventually. Urged by a primitive desire to continue life (human or not), I decided to devote my life to the said goal. I realized this is a risky, life-long endeavour with huge chance of achieving little at best. What is the best strategy for me...

This is the answer I am looking for.

For the four Maxwell equations, only the third one (Faraday's Law) has a proportionality coefficient of -1, while rest have a magnetic constant or electric constant . It doesn't seem like the units of the third law are calibrated to eliminate the constant. So why is the coefficient equal to...

It said the probability of the unchoosen door increased, but it didn't tell why doesn't the probability of the choosen door increase accordingly. May be I missed something?

Doing an exhaustive list does yield the result, but I am not asking for that. I am asking why the probability transfers to one door only.

http://en.wikipedia.org/wiki/Monty_Hall_problem This is a game about probability: Say there is three doors. Two goats and a car are hidden behind. Wanting to pick the car, you randomly picked a door. Then the game host open one of the unchoosen door which happened to contain a goat. And...

Homework Statement A mixture of 1.773kg of water and 227g of ice is in an initial equilibrium state at 273K, in a reversible process, brought to a second equilibrium state where the water-ice ratio,by mass, is 1:1 at 273K. Calculate the entropy change of the system during the process.Homework...

The following is an interpretation of entropy inspired by the video below.I further develop the content and attempt to reconcile the seeming irrelevance of thermo and info entropy. The result is rather successful. Please tell if it works in explaining the equations...