# Search results

1. ### What is the highest a projectile has been thrown or fired from ground level on earth?

http://en.wikipedia.org/wiki/Electromagnetic_gun" [Broken] about rail guns says: the U.S. Navy has tested a railgun that accelerates a 3.2 kg (7 pound) projectile to approximately 2.4 kilometres per second (5,400 mph). It also talks about current research to use this technology to launch things...
2. ### Firing electrons at the nucleus

Thanks Drakkith.
3. ### Simplifying an equation

Thanks AlephZero that helped a lot and saved me a lot of time I might have wasted trying to prove it was.
4. ### Pascal Triange - Fibonacci Sequence

http://en.wikipedia.org/wiki/Pascal_triangle#Overall_patterns_and_properties" but that doesn't really answer your question rather than just state it. I think http://www.maths.surrey.ac.uk/hosted-sites/R.Knott/Fibonacci/fibmaths.html#whypascal" does though.
5. ### Simplifying an equation

I'm having a discussion about blackbody radiation on one of the other forums. I'm trying to prove that two blackbody emitters combine to act like one blackbody emitter. Unfortunately the algebra is beyond me. What I need to show is the following: I want to show that...
6. ### Firing electrons at the nucleus

Why can you fire neutrons or alpha particles at the nucleus and see interesting nuclear effects but you can't fire electrons at the nucleus? Or can you? I would guess not, otherwise electrons would collapse into the nucleus in every day life. I've heard that doesn't happen because it would...
7. ### Derivative of momentum

Another may of looking at it, but reiterating what the others have said, is as follows: p=mv F=dp/dt (Newton's second law states force equals rate of change of momentum) F=d(mv)/dt =mdv/dt +vdm/dt (equation 1) if the mass is constant then the rate of change of mass, dm/dt=0 so this becomes...
8. ### What causes deviations between Sun and blackbody?

I see that two black bodies acting together would behave like a black body with a temperature between the two, but shouldn't it still behave like a perfect black body emitter at the intermediate temperature? Shouldn't the emission spectrum be the weighted sum of the two individual spectrum? Why...
9. ### Matter can neither be created or destroyed

Indeed, physics says (now, though it hasn't always) that there was a beginning. I think even philosophically a beginning is a necessity: If the universe has been around forever and time is linear, then it would take an infinite amount of time to reach this point, which is not possible, "now"...
10. ### When will steam turbines be replaced to directly generate electricity?

Modern steam turbines are quite different from the piston steam engines of James Watt. In modern power stations I believe they work with a thermodynamic efficiency of 80-90%. They do this whilst being relatively easy to maintain and being adaptable to varying amounts of heat energy being...
11. ### Matter can neither be created or destroyed

I completely agree and I hope I'm open minded to new evidence coming my way. I'd be very excited if someone did come along with evidence of something happening before the big bang. Until they do though I've got nothing to believe in that precedes the big bang.
12. ### Matter can neither be created or destroyed

You can ask why and why again, but eventually you have to say "that's just the way it is." You can ask why the big bang happened. It may be the answer is there is no reason for it, that's just the way it is. You might believe that God caused it, but most people who believe in God, if pressed to...
13. ### What causes deviations between Sun and blackbody?

Ozone is located in the lower stratosphere. It absorbs the harmful high frequency UV light. This why the intensity reaching earth at the low wavelength region is less than expected, although it means the phrase "at top of the atmosphere" is misleading. When ozone absorbs UV it splits into oxygen...
14. ### Probability of throwing balls into bins

Ok. I think I've got this. For n balls distributed randomly in N bins, the probability of picking a bin at random and finding x balls in it is: C(n-x+N-2, N-2)/C(n+N-1, N-1) which is the same as (n-x+N-2)!(N-1)!n!/[(N-2)!(n-x)!(n+N-1)!] for 50 balls distributed randomly between 20 bins the...
15. ### Probability of throwing balls into bins

I am part of the way to calculating the numerator but unfortunately here in the uk it's time for bed.
16. ### Probability of throwing balls into bins

It's interesting to note that for 1 bin there is only one way. All the balls go in the one bin. For two cups there are k+1 ways (n=number of balls, k = number of cups) taking 7 balls for some examples: 70 61 51 41 31 21 11 n+1 ways for 3 cups it is the sum of the natural numbers from 1 to...
17. ### Probability of throwing balls into bins

I just wrote a long reply which I lost (that's what comes with being a noob). I have a similar answer to you but slightly different: C((n+k-1),(k-1)) which is (n+k-1)!/(k-1)!(n-2)! This gives 10 for putting 3 balls into 3 cups which is what I mentioned above. Here are the 10 ways: 300 210 201...
18. ### Probability of throwing balls into bins

SW VandeCarr: I like your way of doing this but am having some problems understanding it fully. You seem to suggest a normal distribution around a peak 2.5. I have a problem with this because if you imagine a 3 ball deviation from the mean then you get a problem. Of course it is possible to have...
19. ### A friend of mine did this and Im not sure what it means

I think it means either he has Irish ancestry or he is a Celtics fan :smile:
20. ### Probability of throwing balls into bins

I believe solving this problem is what you do to derive the Maxwell-Boltzman distribution of energies in molecules at equilibrium, although in that case you have a very large number of bins (molecules) and balls (energy). That might be a good starting point for researching for a combinatorial...