CaptainPanic

Correct. So, now you actually already have converted the time units, but from seconds to hours. You just didn't know you can do it already. If I write that I walk 1 meter in 1 second, that's the same as saying I do 1 m/s. So, if I ask you how many meters I then did in 1 hour, then I ask you to go from m/s to m/hr, and you did that without mistake. So, to go from ft/s to miles/hr, you do it in 2 steps: first from ft/s to ft/hr, and then to miles/hr, or the other option is first from ft/s to miles/s and then to miles/hr. I've seen you do both steps correctly already, so I think my work is done here.

b seems pretty close to what I get, but not exactly the same. Also, the question asks for a velocity (which has the unit m/s), and you write acceleration (m/s^2). a and c correspond to what I had.

If I travel 1 meter in 1 second, then how many meters did I travel in 1 hour?

I don't think so. Our atmosphere is 80% nitrogen, which is not stored in huge quantities anywhere else (not in the oceans, not in rocks either). So, remove half of that, and it's just gone.

Sy = 0.5*a*t^2 + V0*t + S0 With the initial speed (V0) is zero, and we set the initial height (S0) also to zero, then we are left with: Sy = 0.5*a*t^2 + 0 + 0 = 0.5*a*t^2 We know a = 9.81 m/s^2, and we know that Sy = 15 meters, because that's in the question. Then you're left with 1 equation, and 1 unknown. So, you have answer a now. In b, I really don't know why you solve for the acceleration if you already know g (that's the gravity acceleration!). But the answer looks ok to me... you've rounded it off differently, I think. And c is above. It is easy to make mistakes with these formulas. If you have made a mistake, it is often easier to start again, on a fresh piece of paper. If you start to search for the mistake you might overlook it a million times. If you start fresh, you might just not make the mistake and you never have to search for it at all.

How many seconds are in an hour? Btw, you probably want one or two more decimals in your conversions from ft and meters to miles.

No, you didn't You used Sy = g*t = 9.81 * 1.5 = 14.715, (which is wrong).

Tell us how you did the calculations so far, because I have the feeling you're not using the correct formulas.

Then don't. Do it one at a time.

Eeh... that's not correct. First you must decide in which unit you will add up all the things (note: it can be miles, but not necessarily). Then you convert kilometers to miles. 40 km = ?? miles --> 40 km/hr = ?? mph ... and in 3 hrs, they therefore did 3*?? miles. Then you convert meters into miles. 20 m = ?? miles But this time, it's in meters per second, so you have to multiply by the number of seconds (how many seconds in 1 hour?). Etc, etc. And finally, you just add up the 1st, 2nd and 3rd leg of the journey.

Story of my life.

Ok - funny question. Writing a sci-fi book or something? If you suddenly remove half the atmosphere (let's say the northern half - the entire northern hemisphere's atmosphere), then the atmosphere on the southern hemisphere would rush north to compensate. At first, the oceans in the north would boil, but when the air from the southern atmosphere would reach the north, that would stop. I have no way to estimate how long that would take, but we're talking minutes to hours, no more - long enough to suffocate. It would be quite a storm though, with windspeeds higher than ever. Afterwards, the overall pressure would be only 0.5 atm, instead of the 1 atm we have now. The initial massive decompression would cool the atmosphere by a good 70 degrees to -50 Celsius (this is a rough approximation!!). I think that also, in this decompression all the water in the atmosphere would condensate or sublimate (form water droplets or ice crystals), so you get a lot more clouds. After a little while, the sun would surely heat the atmosphere again (rough estimate is that this would take about 3 weeks), and these clouds would disappear. A little more water would evaporate, but nothing significant. I don't think that the sea water levels would change much because of it. But during those few cold weeks, the climate would be quite different. Perhaps it could change forever. That could have long lasting implications. If you can survive the initial complete vacuum in the north, then I think you can survive the whole thing actually. 0.5 bar is enough for people. 0.5 bar is the pressure you find between 5 and 6 kilometers altitude. It would take some getting used to, but you can survive there. We'd be tired all the time though.

Ok, so is this normal in the US? We usually don't get too much news here about the lawsuits and court procedures (only the shocking news makes it onto our front pages).

Is it normal to allow victims to influence the charges that the district attorney will pursue? Why are the victims talking to a district attorney, other than for information about the incident, and in court for a testimony? I understand that a victim wants to get a criminal punished for what has been done, but isn't it dangerous to involve these (very emotional) victims in the determination of the official charges? And isn't it even impolite to involve them when they are still mourning, less than a week after the incident? I'm so confused because I read in the news that the district attorney is talking to the Batman shooting victims to determine which charges they will pursue. See, if my 6-year-old daughter had just been shot dead a few days ago in a cinema (one of the victims really was a 6-year-old), you bet I'd ask for the death penalty. Or perhaps a life imprisonment, but with a daily torture. Some old medieval torture wouldn't be cruel enough. But isn't that exactly why the victims are typically not involved in cases like this - certainly not so soon after the event? It is the job of a district attorney to get people punished. But to do that in a civilized way, I think that the district attorney must be a little detached from the case (or at least not be emotionally involved). Isn't that district attorney capable of figuring out which punishment is appropriate by himself/herself? I'm sorry to say, but this sounds a little like a mob rule. Is this normal in Colorado? Or perhaps in the whole USA? I don't think it's normal in the Netherlands, where I live. I mean, it's been in the news now. How can that district attorney not ask for the death penalty now? And please don't get me wrong, I feel really sorry for the victims. It's absolutely awful what happened there... and I know criticising this might make me sound like a heartless bastard, but I'd like to bring it up anyway.

I'd be very surprised if the politicians have to search for these jobs. I bet they're being invited by the companies all the time. It's the companies that seek to get more influence in the politics - not the politicians who want to get rich. This happens on local/state and federal scale (and also in other countries). For a large company, it's peanuts to pay a few thousands/millions to a congresman. And if you employ the congresman, this is not considered bribing. It's completely legal. About the founding fathers... I had a quick look around, and I found that Thomas Jefferson had at least one side job too. While he was also the president of the USA, he was also the president of the American Philosophical Society. I'm not sure if that made him rich or not, but it shows that they probably didn't care too much about side jobs.

That video says that politicians get rich even in times of crisis. Are you suggesting that the CEOs of large companies don't give themselves huge sums of money even in times of crisis? Look at the incomes of the management of the banks that were bailed out. They effectively let their companies go bankrupt, and they were saved by the government. Yet these CEOs get annual incomes of many millions of dollars (here's a link for more info). In addition, the increase of the net worth of the politicians is for a huge part caused by the side-jobs that they do. They are invited by companies to sit on the board of directors, or the management board or something. That's just one of the extremes of lobbying, and I cannot hold individual politicians responsible for that. The entire system is rotten to the core - but it includes all the big business. You state that you don't trust your government because of this. I would go even further. I don't trust companies that knowingly play this game of bribery either. But I disagree with your position to blame it all on the government. It's a whole system (of extreme capitalism) gone wild.

! Moderator Note Nelson, we're all each other's pals on this forum. And even if that is not true, we want people to use such polite words that we don't even notice who are pals and who are not. To read more about how to behave here, you can check our forum rules and especially the etiquette. Don't reply to this moderator note. If you have any issues with this moderator note, take it up with the staff through the report button.

Supercooling your air inlet is a little pointless, because your refrigeration cycle will completely ruin the fuel economy of your car. Also, if you look at the formula of the Carnot efficiency of a heat engine, then you might notice that it only matters what your high temperature is (the hot reservoir, the combustion) and what the temperature of your cooling (the cold reservoir, which is the outside air) is. For Carnot, it is not relevant that you supercool your air first, as this happens within the system, and is therefore irrelevant. Actually, the engine itself might be more efficient if you use the supercooled air as a cold reservoir, but if you look at the whole system, then your only cold reservoir is the outside air.

The market for such things is so tiny (if it exists at all) that you will probably just have to phone someone working at a company that deals with high pressure systems, or perhaps is specialized in the construction of lab equipment and hydrogen lab-infrastructures. Also, it's gonna be heavy. I'd be surprised if it was light enough to build into a helicopter or quadcopter.

! Moderator Note JMJones0424 made a decent post (post #3). I do not wish to get involved in the topic itself, but it seems that his post should enable some discussion. I agree that this thread is not developing well, and many posts seem off-topic. The few decent posts are the only reason it's still open. Now, please either get back on topic or don't post. If you do not know what the topic is, I suggest the latter option. Also, please don't reply to my mod comments, so we don't further derail the thread. If you have anything to say regarding the mod comment, use the report function, or create a post in the Suggestions, Comments and Support section.

! Moderator Note Everybody, get back on topic. In this thread, the amount of science per post went down, while the amount of bitching went up. The bitching stops now.

I'm not sure what you try to say here, but we did explain plenty of times to pmb what's going on. So, I disagree completely with your analysis that we just shut people up. Also, I think my 1st post in this thread actually addresses the issue that was raised (originally) in the OP. Then again, maybe "mod" does not refer to the moderators here, and "pourmonbien" might not refer to pmb.

Well, I guess the opening post shows what happens if you ignore people in a discussion. Deleting a post after multiple people replied has the same effect: Suddenly the replies that follow just don't make any sense anymore. This might be the only time in the history of SFN when the act of deleting a post was actually on topic.

One cannot have a fruitful discussion whilst ignoring a selection of the participants of that discussion. If you want to ignore people, then stop reading their posts.

Science says that the world will NOT end in 2012.