Recent content by cfung

Calculate the polarizability "a(lpha)" of atomic hydrogen in terms of R Homework Statement A simplified model of a hydrogen atom is that the electron cloud is a sphere of radius R with uniform charge density and total charge -e (The actual charge density in the ground state is nonuniform)...

This is what I know about the structure of the universe. In our universe there are 2 parts. The observable part, like many have said, is +/-13.7 billions light years long. Then outside the observable you've got the unobservable part of the universe. It's unobservable simply because light isn't...

Come on, one learns nothing from the 2 statements above. (Sorry I am curious to know too) How are they related, and, if the 1st law includes the 2nd then what is the derivation?

This happens most often to discussions that involve non-provable subjects. Not all physics concepts are so, at least I believe. Einstein once said, "Imagination is more important than knowledge." I take this to say, "To have a feeling of what momentum is is more important than to state p = mv."...

If I were to explain why water is a better thermal conductor than air, I would say because liquid are denser than air (molecular distances are small) thus giving water more opportunity to contact with the heat source. There are rarely proofs in physics theories, if any. But explanation like...

Absolutely wonderful for both the question and solution. It's delightful for me, too, to realize that all that 80 celcius worth of kinetic energy in water are absorbed by the ice in order to cause a phase transition from 0 celcius solid to 0 celcius liquid. It'd be wonderful to see this in...

I may have used the wrong diction, pardon me for that, but in that context I meant force as being "propagated". Though thank you for your clarification on the subject of impulse.

According to (Force)*(Time) = (Impulse), if 50 Newton is exerted on the 2kg mass through a string in 0.5 seconds, then the hanging mass's change of momentum would be 25kgm/s. Likewise, if in an experiment one pulls on the string with 50N tension and the string takes 0.5 seconds to completely...

Cool, the conclusion is to attribute the break of the string to the overwhelming stretch in the string's molecular structure, albeit rapid. It's a sensible explanation I should accept. Thanks.

If it were possible that only some percentage of the force applied becomes effective to the system, then this really explains. And it's somewhat convincing because it's very ordinary to lose energy in a system. But it's difficult to imagine a nearly massless string would lose significant amount...

I read the brief history of time by Hawking and somewhere in that book the author talks about exactly this idea of your concern. With great clarity, he points out the consequences of Newtonian absolute space time and explains how it is flawed with Einstein's theory. Let me see if i can bring...

True and worthwhile to point out. In general, the top string feels 20N more tension is always true when the mass is in any uniformly accelerated frame of reference at 10m/s^2, as this demonstration has assumed.

First, thanks for your reply. Now, you stated "If the rapidly increasing pulling force is sufficiently fast, there will be a surge of tension on the lower string, enough to break the string," which is the farthest I could arrive and it's exactly the part where I can't be confident. Because...

Just thinking about the problem empirically, it seems impossible for the bottom string to break (Note it can be assumed that both the strings break at an identical tension value). This is because no matter how much force you exert on the bottom string, the top string will always experience 20N...

The demonstration: A mass of 2kg is hanged to a string that is hanged vertically from a fixture. Another string is attached to the bottom of the mass and then this bottom string is given a downward pull. Note that the strings used are assumed identical. This demonstration can be found here...