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# Physics: Decimals can't be infinite because the space between must end. - Page 3

Quote:
Originally posted by sunilraman
Quote:
Originally posted by max_naylor
I'm glad I've given up maths in college. Although I am doing physics. Poo.

Can you answer my deceleration question please? Nobody else here feels like doing it: Two objects start moving at each other, 1/4 of the distance each second. Initial distance between two objects is 1 metre at 0sec. At 1sec, distance 0.5 metres, 2sec, distance is 0.25sec, etc.

What is the rate of deceleration of each object in metres/(second squared)?

I'm sorry I have no idea what your talking about. I haven't actually started college yet, I've just left secondary school! So what you're asking is beyond the scope of a GCSE textbook by the sound of it. I hope someone else has managed to answer your question. (I meant sixth form college, I'm only 16 on the 21st!!!, college means uni over there doesn't it? Ask me in two years time and I may be able to tell you )
[QUOTE]Originally posted by Mac_Doll
Bwahahaha!! You started this thread, CosmoNut, and like you and I predicted, all the lovely math nerds came out of the woodwork. I love it.....I say to Hell with Math... I'm an art major.

Heh. All the bloody art majors at my college/university only had classes 3 days out of 5, most of those only like 9am-1pm or 1pm-6pm or something like that...!

I had 5 full days in a week. A few 3 hour practicals each week.

I majored in Biology[Molecular] - 3/4s of my degree. The other 1/4 was IT. SmallTalk/ Ada95/ SQL/RDBMS theory. At least the SQL/RDBMS had some practicals in Access. The coding stuff, oh had one C programming class. A pity they didn't teach anything practical like ASP or Cold Fusion. Heh. PHP was not even on the horizon back then.

*sigh* My IT stuff at Uni was high-scoring, but I did only a few cherry-picked subjects here and there. Not enough to really make a career out of it except for web design for a few years!!! Now though with server admin and MCSE CCNA and whatever the hell the whole IT industry looks weird to me.

Well, that's what happens when you major in Molecular Biology (enzymes, DNA, RNA, protein folding, blah blah blah) and end up HATING it and trying to cobble together a career in Web Design....

Not to mention all the self-learning Photoshop and Illustrator and GOOD graphic design AND self-learning about art movements (Dada, Surrealism, etc) \ Did some bad (bad as in bad not bad-ass) Lightwave 3D stuff for a bit....

Yeah, F**K Math. Last class I did was back in '95. At college/uni the only Math we needed in Biology was more the Biochemistry stuff like calculating concentrations of mixtures and chemicals and stuff.
This discussion would not be complete without the discussion of Planck Units. http://en.wikipedia.org/wiki/Planck_units

"...At lengths and times of less than approximately one Planck unit, quantum theory as presently understood no longer applies."

Smallest length in the universe - 1 Planck unit approx. 1.61624 × 10^-35 metres

Smallest time slice in the universe - 1 Planck unit approx. 5.39121 × 10^-44 seconds

Just wanted to add this to the discussion as one of the Physics' view of super-duper-tiny (yes this is a highly technical term) amounts of time and length.
Quote:
Originally posted by Hiro
Now you just exposed yourself as espousing bullcrap. How much else have you made up? Lingo can't save you from that gaffe.

The fatal counterexample: an acceleration step function. No movement until 33.5 sec (later than your log result), then constant velocity (instantaneous infinite accel) and immediate decel back to zero velocity. Your log function computes an incorrect time because it implicitly assumes a smooth non-kinked acceleration function. It can't take into account that movement may not even commence until after the smooth functions result, leading to an obvious contradiction.

The fact infinite accel is theoretically impossible is of little consequence since there are still an infinite number of other accelerations that can also be applied after 33.5 sec that will get our object to the correct point at 34 sec, but it only takes a single counterexample to prove your statement false.

You are trying far too hard to prove me incorrect. It is actually pathetic.

My statement is completely true: acceleration doesn't matter if the object ends up at the same spot at the same time.

Oh, and the distance dependence of one of the moving objects (the one moving in the positive direction) is:

d= 1/2*(1-2^-t)

The derivative gives us the instantaneous velocity:

dd/dt=V(t) = (1/2)*(2^-t) ln(2)

The second derivative gives us the acceleration:

dV(t)/dt = -(ln(2)/2)^2*(2^-t)

So yes, as hiro said the acceleration is not constant, but of course we knew that without doing the math - constant acceleration never lets an object in motion come to rest at t= infinity.

Sorry it took me so long to respond, I had a long day in lab yesterday.

Edit:

Similar results for object moving in negative direction:
d=1-1/(1-2^-t)
V(t)= -(1/2)*(2^-t) ln(2)
A(t)= (ln(2)/2)^2*(2^-t)
"In a republic, voters may vote for the leaders they want, but they get the leaders they deserve."
"In a republic, voters may vote for the leaders they want, but they get the leaders they deserve."
[QUOTE]Originally posted by sunilraman
Quote:
Originally posted by skatman
The distance between objects at time = t (sec) is 1/ (2^t) meters. Acceleration is second derivative of distance function.
That's twice the deceleration of each object.
I'll let you ponder the simple derivative. :-)

Sorry skatman, can't process this stuff. Why can't anyone tell me what the deceleration of the object in metres per second squared?

*All I remember is that if you have an acceleration curve, you differentiate at a certain point you get velocity.... or something like that.

Time derivative of the acceleration function is called a "jerk".
To get the velocity, you need to integrate the acceleration function with respect to time.
Quote:
Originally posted by hardeeharhar

You are trying far too hard to prove me incorrect. It is actually pathetic.

My statement is completely true: acceleration doesn't matter if the object ends up at the same spot at the same time.

What you say in the last half of the last quoted sentence is true. But that isn't what your value of t=33.2192809 represents from this post:

Quote:
In response to how would one calculate how many steps you would have to take to get 1 A separation:

log (10^10)/log(2) = 10*1/(log(2)) = 33.2192809 (looking up on a log table )

That is explicitly for some intermediate point between time step sample points that happens to be at 1 Angstrom distance.

It's easy to be pissy and indignant when you move the goal posts, but when everyone looks you are someplace "over there" (wherever that is) waving your arms furiously, while the goal is really still right where it is all along.
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Who is using lingo now?

Goal post, waving arms?

Come on, any intelligent reader can come to the realization that quite literally 33.something is in between 33 and 34. If you parse the steps in units then you have to round up. If you parse the steps in decimals, then you can provide how ever many decimals you feel like providing. Regardless, my answer is absolutely correct to the nth place, and I have left it up to the Intelligent reader to figure out where they parse.

(honestly, I think you are just pissed because you forgot how logarythms work)...
"In a republic, voters may vote for the leaders they want, but they get the leaders they deserve."
"In a republic, voters may vote for the leaders they want, but they get the leaders they deserve."
sunilraman: Oooh, you're a Biology major. I was one too, before I changed it to Art. I was going into Zoology. I figured that my artistic talent is more rare than knowledge of the animal kingdom. I still adore science though.
Resident Furry, Animation student, and Steve Jobs fan.
Resident Furry, Animation student, and Steve Jobs fan.
Quote:
Originally posted by hardeeharhar
Who is using lingo now?

Goal post, waving arms?

Come on, any intelligent reader can come to the realization that quite literally 33.something is in between 33 and 34. If you parse the steps in units then you have to round up. If you parse the steps in decimals, then you can provide how ever many decimals you feel like providing. Regardless, my answer is absolutely correct to the nth place, and I have left it up to the Intelligent reader to figure out where they parse.

(honestly, I think you are just pissed because you forgot how logarythms work)...

I don't know if I should admire your single-minded persistence in the face of adversity, or pity you for abject self-inflicted cluelessness. It's kinda sad because you obviously have some smarts, but have your ego filters so tight you can't see, or at least acknowledge, your error.
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Quote:
Originally posted by Hiro
I don't know if I should admire your single-minded persistence in the face of adversity, or pity you for abject self-inflicted cluelessness. It's kinda sad because you obviously have some smarts, but have your ego filters so tight you can't see, or at least acknowledge, your error.

Aren't we the condescending one?

These statements from someone who has attempted to suggest my answer was a representation of something more than just an answer.

Edit: Removed gratuitous go away.... You should know better than to continue...
"In a republic, voters may vote for the leaders they want, but they get the leaders they deserve."
"In a republic, voters may vote for the leaders they want, but they get the leaders they deserve."
Quote:
Originally posted by hardeeharhar
Aren't we the condescending one?

These statements from someone who has attempted to suggest my answer was a representation of something more than just an answer.

Edit: Removed gratuitous go away.... You should know better than to continue...

Hit a nerve did I? Accuracy sucks, doesn't it.
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Quote:
Originally posted by Hiro
Hit a nerve did I? Accuracy sucks, doesn't it.

No, not really. As someone who has been called condescending throughout my adult life, I enjoy spreading the love.
"In a republic, voters may vote for the leaders they want, but they get the leaders they deserve."
"In a republic, voters may vote for the leaders they want, but they get the leaders they deserve."
[QUOTE]Originally posted by Mac_Doll
sunilraman: Oooh, you're a Biology major. I was one too, before I changed it to Art. I was going into Zoology. I figured that my artistic talent is more rare than knowledge of the animal kingdom. I still adore science though.

Heh. It was kind of weird. On one hand I had read and watched A LOT of sci-fi growing up (though not as much as most on these boards ) so I was like DNA-this and genetic-that and that was all cool with the Molecular Biology and Biochemistry stuff.

On the other hand I was doing Botany, Ecology and (very basic) Zoology. To like, save the world, man..... like, dude..... check out these flowers, man.... whoaa.... One of the Ecology 101 assignments was to go off to an island off Brisbane, Australia (Stradbroke Island) and count the number of trees or some shite like that. And I was, how do we save the world doing this nonsense? Like, dude, where's the environmental activism?

So yeah in my fourth and final year of college I pursued the genetics part heavily and a lot of mice died in the name of science and a lot of frog tadpoles were genetically mutilated via DNA type injections. When I graduated I was like, f**K this and did web design for a few years.

2003 I actually worked at Greenpeace in Australia doing web admin/ design and was finally, like Fighting The Power, man.....

Then I went off and wanted to be an artist and 2004 was all over the place. My artistic talent was too heavily tied in with my emotions and spiritual outlook. Not sustainable Making a living from my artistic talent was incredibly stressful, dude.

2003 at Greenpeace was a kinda cool job though. Not as hippy as you think, and not as corporate-environmentalism as you might fear. But my parents just did not understand WTF I was doing and that it was like, a real job, man....
Weird thing. I'm like an idiot savant sometimes, knowing some stuff about this here and this that but can't do other things. I'm happy to have somehow "predicted" the 50-cent-Apple thing and brought the infinite-numbers discussion here into the subatomic physics realm. But a lot of empty spaces in my knowledge and understanding. Like you peoples that did the derivative thingy to get an expression for the deceleration of the objects, that was 1337, man....

Anyway, love you all, spread the AppleInsider love.... Hiro and HHH, let's not fight man, let's spread the intellectual love, man.... yeahhhh Have a spliff between you two and all will be chilled man.... yeahhhh
Quote:
Originally posted by hardeeharhar
No, not really. As someone who has been called condescending throughout my adult life, I enjoy spreading the love.

Just two peas in a pod...
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Quote:
Originally posted by blackbird_1.0