Recent content by nitai108

Hello, I need to transmit motion at a 90° angle, I was considering worm gears or bevelled gears, but then I thought about a flexible drive shaft, it would be cheaper and wouldn't have any backslash issues. I need to transmit motion at a 90° angle with a low toque and low RPM, the application...

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Feynman makes an example (15-6 in his lectures) about failure of simultaneity at a distance, using the Lorentz's transformation of time. A man moving in a spaceship (system S') synchronizes two clocks, placing them at each end of the ship, by a light signal sent from the middle of the ship, and...

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Thanks for the replies! I was reading Feynman Lectures and I searched Newton second law to see if it could be used in a variable mass system, of course wikipedia came first and there are a few notes which state that the law is valid only for constant mass systems (note 20 21 22...

Newton's second law states F = d(mv)/dt as this law is valid only for constant mass systems it is also written as F = md(v)/dt. But let's suppose the mass was not a constant, then the derivative of the law would become F = m'v + mv' (where by ' I mean derivative, m' = dm/dt), would that be...

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Because light can only slow down if it passes through objects (such as air or glass) but in the vacuum it's always c, right?

If a car is traveling towards you and turns on the lights the speed of light would be c, but if the car was traveling away from you and turned the lights on would the speed of light be c or less than c? I've tried to search this question, but it's not easy to describe in a search engine!

Thanks for the help. I still don't understand the (n + 1), where does it come from? I've tried to search the net, and my textbooks but I never found examples of (xn)!, only n! = n(n-1)!.

Can somebody please explain to me this simplification and how it's done? \frac{n!}{(2n)!} = \frac{1}{(2n)(2n-1)...(n+1)} Thanks a lot.

Ok, thanks a lot.

Thanks tiny-tim, and thanks Random Variable, I did solve them pretty easily with the Stirling's approximation. Is there any other way to solve them, without Stirling's approx.?

Hi, I don't undestand this limits to infinity. [ (2n)! / (n!)^2 ]^1/n and [ ( n^n + 2^n ) / (n! + 3^n) ]^1/n I've absolutely no idea how the first one can be "4", and the seconda one "e". Assuming (1 + 1/n)^n = e I don't see how can I go from that form to this one. Any...