# Kedas

Senior Members

695

1. ## time in relation to volume of alcohol

Just a few remarks: -The alcohol that is still in your glass doesn't have an effect on you while alcohol is already broken down. -If you drink your beer with a straw the alcohol will be obsorbed faster. (although the amount will be the same)
2. ## I've looked everywhere.

I don't know much about chemistry anymore but isn't that image showing you the chemical structure?
3. ## Simple car physics, find the mistake.

If I'm not mistaken this are the forces that pull the car. (without losses and at 1900tr/min 250Nm) 1st, 1/3.42, total 1/14.35, 250Nm*14.35=3587Nm on the tire, /0.3 = 12000N 2nd, 1/2.11, total 1/8.84, 250Nm*8.84=2210Nm on the tire, /0.3 = 7367N 3rd, 1/1.43, total 1/6.00, 250Nm*6=1500Nm on the tire, /0.3 = 5000N 4th, 1/1.09, total 1/4.57, 250Nm*4.57=1143Nm on the tire, /0.3 = 3810N 5th, 1/1.10 total 1/3.64, 250Nm*3.64=910Nm on the tire, /0.3 = 3033N 6th, 1/0.91, total 1/3.02, 250Nm*3.02=755Nm on the tire, /0.3 = 2516N
4. ## Simple car physics, find the mistake.

Torque doesn't change with an higher gear but the ratio decreases resulting in a different force on the wheels for every gear, the higher the gear the lower the force on the wheels. (lower acceleration) A higher gear is the same like putting a bigger wheel on your car. Torque is the same but an increasing radius reduces the force. (Torque/radius=force) 6 gear system (fixed ratio:1/4.2) 1st, 1/3.42, total 1/14.35 (3.42*4.2) 2nd, 1/2.11, total 1/8.84 3rd, 1/1.43, total 1/6.00 4th, 1/1.09, total 1/4.57 5th, 1/1.10 total 1/3.64 6th, 1/0.91, total 1/3.02 ('total' is the ratio between the engine and the wheel) Ratio diff. between first and second is 1.6 so the force drops with a factor 1.6 when it's put in second gear. (assuming a constant torque of the engine) So the assumption of a more or less constant acceleration is wrong. We would need to known when they changed gear to compare engine torque with this 0-80km/h timing of 8sec.
5. ## Simple car physics, find the mistake.

The engine rotation speed of 1900tr/min isn't used in the calculation. It is assumed to be more or less constant resulting in a more or less constant torque of 250Nm. The torque varies a little with the rotation speed. But you have won one point for trying
6. ## Simple car physics, find the mistake.

We are looking for a torque of 4200N*0.3m=1260Nm Specifing the torque of an engine per wheel would be odd but that would get us close, 4*250Nm or 1000Nm.
7. ## Simple car physics, find the mistake.

Given data: 250Nm @ 1900 tr/min. (TDI 1.9L engine, VW Jetta 2006) 0-80 km/h (0-22.2m/s) in 8,0 sec Car weight: 1384Kg (empty) adding a person and fuel lets say 1500kg We can assume that the car speed is rising more or less linear between 0 and 80km/h. That is even logical if an automatic gear is trying to keep the tr/min around 1900tr/min resulting in a constant torque generated by the engine. The calculation: The average acceleration of the car is measured at 22.2 / 8 = 2.8 m/s² The needed average force to get this acceleration is 1500kg*2.8m/s² = 4200Newton (m*a=F) The torque is 4200N*r=250Nm --> r = 0.06meter (6cm) So what went wrong what does this 6cm mean? It isn't even remotely close to the tire radius although this 4200N should be present on the tires (2100N each) if you want an acceleration of 2.8m/s².
8. ## Does Digital TV make it easier for other intelligent lifeforms?

I didn't know where to put it, so I had to choose... The ability of an other intelligent being to undestand something alien isn't really computer science. If I would give you a stream of ones and zeros in a file with the info it's a known file format you would still have a hard time figuring out what's in there. For an other intelligent being it's even worse. It's like giving this file to someone without (much) knowledge about computers. (could be your mother ) That person is an intelligent being but I'm putting my money on the fact that he/she will never figure it out without help. So if we turn things around how much chance would you give us to figure out the meaning of an signal that we receive? Shouldn't that be more or less same chance? (extremely low)
9. ## Does Digital TV make it easier for other intelligent lifeforms?

yeah but it's not like there is a tag in their own language attached saying this is video, from their point of view it's just a stream of ones and zeros.
10. ## Does Digital TV make it easier for other intelligent lifeforms?

Now that we also sending more digital TV around. I was wondering would it be easier, or more difficult for an other intelligent lifeform to reconstruct an image from it.
11. ## Air's Weight

Take a glas with water and a straw in it. Drink from it via the straw. If the weight of air didn't press the water in your mouth it would not be possible to drink from it.
12. ## The concept of 'unatural'.

useally if people say unnatural they mean there is an other way that isn't designed/manipulated by us. But we are already having so much influence in how things are that it's probably difficult to find something that is really 'natural' it's just not that obvious that we changed it. and yes there isn't really something like unatural since we are part of it. unatural is a result of our god complex
13. ## How do we think?

just my opinion If you figure out how a stone is rolling of a mountain then you have also answered your own question. You say that isn't the same, well having an other set of relations doesn't mean it's executing them differently so it 'thinks' the same . about free will I don't believe it exist, but the fact that we wonder about it proves that we assume that it exist. An illusion only exist if you created/have more than what there is. since we can't create/change the laws of nature, nor free will nor illusions exist. (but we gave both words a meaning anyway) This message is only here because you pushed me of the mountain.
14. ## Quick LaTeX Tutorial

What's wrong why can't I see a formula here? This is generated with matlab 6.5, command Latex(S). $-\sin(\left({\it Patm}\,t-\arctan({\frac {{\it Pstart}}{\sqrt {-{{\it Pstart}}^{2}+{{\it Pin}}^{2}}}})\sqrt {{\it Kv}}{\it Volume}\right){\frac {1}{\sqrt {{\it Kv}}}}{{\it Volume}}^{-1}){\it Pin}\,\cos(\left({\it Patm}\,t-\arctan({\frac {{\it Pstart}}{\sqrt {-{{\it Pstart}}^{2}+{{\it Pin}}^{2}}}})\sqrt {{\it Kv}}{\it Volume}\right){\frac {1}{\sqrt {{\it Kv}}}}{{\it Volume}}^{-1})\sqrt {{{\it Pin}}^{2}{\it Kv}\,\sqrt {-{{\it Pstart}}^{2}+{{\it Pin}}^{2}}\left (-2\,\sqrt {-{{\it Pstart}}^{2}+{{\it Pin}}^{2}}{{\it Pstart}}^{2}\left (\cos({\frac {{\it Patm}\,t}{\sqrt {{\it Kv}}{\it Volume}}})\right )^{2}+\sqrt {-{{\it Pstart}}^{2}+{{\it Pin}}^{2}}{{\it Pin}}^{2}\left (\cos({\frac {{\it Patm}\,t}{\sqrt {{\it Kv}}{\it Volume}}})\right )^{2}-2\,{{\it Pstart}}^{3}\sin({\frac {{\it Patm}\,t}{\sqrt {{\it Kv}}{\it Volume}}})\cos({\frac {{\it Patm}\,t}{\sqrt {{\it Kv}}{\it Volume}}})+2\,{\it Pstart}\,\sin({\frac {{\it Patm}\,t}{\sqrt {{\it Kv}}{\it Volume}}}){{\it Pin}}^{2}\cos({\frac {{\it Patm}\,t}{\sqrt {{\it Kv}}{\it Volume}}})+\sqrt {-{{\it Pstart}}^{2}+{{\it Pin}}^{2}}{{\it Pstart}}^{2}\right )^{-1}}{\frac {1}{\sqrt {{\it Kv}}}}$ -\sin(\left({\it Patm}\,t-\arctan({\frac {{\it Pstart}}{\sqrt {-{{\it Pstart}}^{2}+{{\it Pin}}^{2}}}})\sqrt {{\it Kv}}{\it Volume}\right){\frac {1}{\sqrt {{\it Kv}}}}{{\it Volume}}^{-1}){\it Pin}\,\cos(\left({\it Patm}\,t-\arctan({\frac {{\it Pstart}}{\sqrt {-{{\it Pstart}}^{2}+{{\it Pin}}^{2}}}})\sqrt {{\it Kv}}{\it Volume}\right){\frac {1}{\sqrt {{\it Kv}}}}{{\it Volume}}^{-1})\sqrt {{{\it Pin}}^{2}{\it Kv}\,\sqrt {-{{\it Pstart}}^{2}+{{\it Pin}}^{2}}\left (-2\,\sqrt {-{{\it Pstart}}^{2}+{{\it Pin}}^{2}}{{\it Pstart}}^{2}\left (\cos({\frac {{\it Patm}\,t}{\sqrt {{\it Kv}}{\it Volume}}})\right )^{2}+\sqrt {-{{\it Pstart}}^{2}+{{\it Pin}}^{2}}{{\it Pin}}^{2}\left (\cos({\frac {{\it Patm}\,t}{\sqrt {{\it Kv}}{\it Volume}}})\right )^{2}-2\,{{\it Pstart}}^{3}\sin({\frac {{\it Patm}\,t}{\sqrt {{\it Kv}}{\it Volume}}})\cos({\frac {{\it Patm}\,t}{\sqrt {{\it Kv}}{\it Volume}}})+2\,{\it Pstart}\,\sin({\frac {{\it Patm}\,t}{\sqrt {{\it Kv}}{\it Volume}}}){{\it Pin}}^{2}\cos({\frac {{\it Patm}\,t}{\sqrt {{\it Kv}}{\it Volume}}})+\sqrt {-{{\it Pstart}}^{2}+{{\it Pin}}^{2}}{{\it Pstart}}^{2}\right )^{-1}}{\frac {1}{\sqrt {{\it Kv}}}} Edit: OK, found the error. In which program can I make a pretty formula based on this latex? There is a pretty command in matlab but it's not graphical.

16. ## Stardust Mission, a success! ;))

I read it's going to be sent to about 150 different places for study.
17. ## Stardust Mission, a success! ;))

Update: http://www.space.com/scienceastronomy/060119_stardust_results.html What is the chance that we caught a frozen virus?
18. ## SD cards.

I would make a backup with a card reader on the PC, format it (correctly) and put the backup back and see what happens.
19. ## Speed of brain decay.

I already saw an article about it a weeks ago (But I didn't had a reference on the net) http://www.newscientist.com/channel/health/mg18925351.200 Basically the cels go in some sort of standby mode and stop using oxigen. This is researched to put someonme on 'hold' do an operation and then start up again. (not having a beating heart makes operating a lot easier) It's simular with animals in winter sleep. So when does time kill you? When there is enough oxigen present to make the cels 'think' that they have to work but too litle to do the job right.
20. ## Quantum Trickery: Testing Einstein's Strangest Theory

Any chance that all particles in the universe are entangled we just don't know which with which. And how to disprove something like this?

22. ## Cosmic Background Radiation is sum of the stars

If we couldn't detect it I wouldn't talk about it. It traveled quote some distance so it's old so what's the problem? Did the universe stop creating this low frequency?
23. ## Cosmic Background Radiation is sum of the stars

Just an idea: Space is limited without edges like a globe surface in a 2D world. If that is true isn't it possible that this background radiation is just the sum of the light from all the stars... If light is going in any direction and it isn't changed from direction then it should end up at the same place after it traveled a long distance in space. (like a rocket around the earth in a 2D world) long waveslengths and long distances go hand in hand. any reasons why this can't be possible?