h a l f b a k e r yThe leaning tower of Piezo
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A very simple idea. We've all wanted to drop a penny from the top of a skyscraper. How much would we be willing to pay for the privilege? Vending machines could be installed in the observation deck of a skyscraper, which would allow us to do exactly that. For the reasonable price of 51 cents, this
vending machine would send that penny rolling down a slot through the wall, and out over the unsuspecting city. The observation deck gets the additional revenue (from the 50 cents it keeps), and we get to fulfill a childhood fantasy. A photo or a DVD of your penny striking the ground would be available for an additional fee.
Terminal velocity of a penny
http://www.gantless.com/paper.html
20 - 45 mph according to this. [Worldgineer, Oct 04 2004, last modified Oct 21 2004]
Jim Carson: Monday morning armchair physicist
http://www.jimcarso...chives/000148.shtml
Looking at the way a penny drops. 23.6 mph to 73.3 mph. He also mentions the TV programme 'Mythbusters' where they fired a penny at somebody's backside at a speed of 64mph with no major consequences. [st3f, Oct 04 2004, last modified Oct 21 2004]
Thar She Blows!
http://msnbc.msn.com/id/4096586/
I wonder if it will be friends with me. [gnomethang, Oct 04 2004, last modified Sep 29 2006]
BalloonDrop.com
BalloonDrop_2ecom
[Shameless plug] [Klaatu, Aug 28 2008]
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I bunned this, but will only keep it assuming one of two things:
1) You have a fenced off penny landing area, possibly containing things like watermellons and glass bottles to destroy.
Or:
2) You move this to the public: evil category. |
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I want my photo in monochrome, just a slow enough shutter speed for some blur, then a strobe to freeze it on the bounce. |
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How about adding a target zone with something breakable in the center. There would be ten second count down and a warning siren to attract a crowd. |
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I do like the addition of breakable targets and a target area. The best I could think of was cheap parking near the building. |
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I'm assuming the attraction is the myth that a penny falling from a skyscraper will reach lethal velocities, which is not true at all. While the zero-drag (vacuum) speed would be quite high, since the penny falls through air, we can't assume vacuum. Terminal velocity of a penny in air (this is the point where drag=weight) is roughly 65 mph, give or take a few. Getting hit wouldn't hurt any more than if someone had thrown it really hard. |
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Can there be another shute for frozen peas? I've heard that if you drop one off the Eiffel tower it could kill someone. When I visited the Eiffel tower as a child I was very uncomfortable walking around underneath it in case some one was testing the whole pois theory. |
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//Getting hit wouldn't hurt any more than if someone had thrown it really hard// |
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+ for the research ... although that's right out of keeping with the bakery as a whole. An idea with proof... what is the world coming to!? |
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// whole pois theory // what is she on this evening? |
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But 45 mph accidents [scout] involve collision between two cars, one of which you are in. You are surrounded by a metal cage which can absorb the impact. Falling off a skyscraper involves a collision between your (soft) body and the (hard) pavement. |
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Actually, it's closer to 200 m.p.h. not enough to "go, like, fifty feet into the ground" but enought to go like through a skull (for example). |
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Oh, I see, a tall building is "at least 40' " according to the link. Here in NYC that's called a speed bump. Also, terminal velocity is the max it can reach (with the air drag) not what it gets to at the bottom. Your penny is accelerating until it hits something. It reaches terminal velocity after approximately 1200 feet, I believe (we did this calculation when I was wee one in high school and I'm not really up to doing over now) |
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Terminal velocity is different for different objects, depending mainly on the shape texture and weight of an object. |
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Indian head pennies, or Lincoln pennies? |
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//shape texture and weight of an object// |
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<looks critically at [Worldgineer]'s head> |
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I was wondering how older heavier pennies would fare in this test. Also, would the slot it rolls down spin the penny fast enough so that it has a gyroscopic effect, causing it not to tumble? What if we could drop dollar coins? So many questions... |
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Could it have a solid steel plate to land on and an automatic retrieval service? It could be like the penny-mashing devices at tourist traps. Take your deformed penny with you as a keepsake from your venture to the city center. |
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Worldgineer's link is interesting. Unfortunately, despite taking a series of measurements, the final conclusions look as though they are reached using intuition, which is a pity. The experimenters look at different modes of falling but I'm not convinced that they cover the full range. |
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The terminal velocity of a penny should vary greatly depending on how it falls. A penny falling completely flat (unstable and unlikely but theoretically possible) shows large flat surface to the air and would fall slowly. Picture driving along with a billboard secured to the front of your car and try to imagine what your top speed would be. |
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Conversely a penny falling on edge (more possible, fairly stable and more likely over a long drop). It now exposes only its edge as a drag surface and will have a much higher terminal velocity. Picture the same advertising hoarding stuck flat to the side or roof of your car. |
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Here are some numbers for a UK penny:
Thickness: 1.7mm
Diameter: 20.0mm
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Area presented edge on: 34.0mm^2
Area presented face on: 314.1mm^2
Added to this the edge profile slopes away reducing drag whereas the face end abruptly at the edge of the coin. |
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Since drag is proportional to surface area I would expect a variation of at the very least a factor of nine in the drag, possibly many more times this as shape is very important in aerodynamics. (Does anyone have coefficients of drag for a flat disk edge on and face on?). |
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OK, my turn to pluck some results out of the air. Say the drag is 20x more flat then on edge, I would expect the fast terminal velocity to be about four or times faster then the slowest. Unfortunately this doesn't give me the much of an idea of where the range starts and finishes. It could be 10-50mph or 20-100mph. Either way, I think that the range would be bigger than that stated in Worldgineer's link. |
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Wow. That rambled on longer than I expected. Let me say that I think it's a great idea and I'd love to look at the bottom end of the penny drop (side on through reinforced glass) to see the coins bouncing off concrete. (goes off to find website with some more numbers on it) |
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I like this too. Similarly when you
take your car to the scrapyard, they
shouldn't just put it in a pile with
the others, they should use some
sort of catapault to 'drive' it into
another car. |
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This would be good in Las Vegas with a silver dollar slot machine on the bottom floor of a tall building. Every once in a while a player would get (un)lucky and be hit by a torrent of heavy coins from the roof. |
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[st3f] I sheepishly admit not reading my link before posting it. Glancing at it again it seems like a high-school level experiment that was poorly planned and therefore went awry, and instead of admitting they didn't consider the theory before designing the experiment they just gave estimates that fit their observations. |
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I liked it because it had experimental data, and I can't find any elsewhere. |
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Anyway, could we choose what it landed on? Lots of people seem to like the breakable target. I think jello or silly putty would be even cooler. |
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It could be a lot of fun to put some ballistic gel samples in the target area. If yours hits the ballistic gel, you could buy that in the gift shop. |
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//Can there be another shute for frozen peas? I've heard that if you drop one off the Eiffel tower it could kill someone. When I visited the Eiffel tower as a child I was very uncomfortable walking around underneath it in case some one was testing the whole pois theory.// |
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Considering the Eiffel Tower curves as it goes up, a frozen pea dropped from the top would hit the structure before it reached the ground. |
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// Well, I for one don't believe all of that "terminal velocity" stuff. // [scout] |
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Scout, this is science. your beliefs are irrelevant.
I'd gladly stand at the foot of any skyscraper while someone dumps a handful of pennies off the edge, just don't ask me to look up...my eyes are softer than my skull. I'll charge a dollar for every penny that manages to hit me, as I expect it to sting quite a bit. Terminal velocity is different for different objects. A skydiver (terminal velocity of 120 mph, approx, and I should know...) will fall faster than a penny (terminal velocity of between 25 and 75 mph, approximately, depending on how it's falling) because the skydiver has less drag per unit mass than the penny. Edge-on, unless the penny is spinning, will actually be a very unstable position. |
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If you're saying fluid dynamics isn't science, then it's nice to meet you Mr. Hawking. |
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It does curve [GenYus] but it has an open structure so you could get a pea through the ironwork of the tower. Or you just throw it out a bit. Alternatively you could throw your pea down the hole in the middle of the tower, but this is only on the first stage and probably wouldn't be high enough to kill. |
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// //this is science// // |
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Not yet. So far just a lot of highly informed conjecture.
There's potential for some real science here, but that'd
spoil the fun. Meanwhile, I'll contribute the following. A
BB (solid copper sphere about, what, 3-4mm?), shot into
the air with a Daisy spring rifle, streaks upward,
disappears for a few seconds, and streaks back down. It
can be safely bounced off the palm of one's hand. Stings
like a wasp, but does not break the skin. (Please wear
safety glasses if you try this at home). I have no idea how
high the BB goes, but the combined drag on the way up
and down is probably near that encountered on a
skyscraper. I never had the guts to put my hand over the
end of the rifle, to compare the impact straight out of the
muzzle, but from what it did to plywood at 10 ft, and that
unfortunate bluejay, I bet it breaks the skin. |
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I'll stand under the penny. |
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Every drop of rain that falls... |
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Consider this: that penny has passed through many hands (and probably some kid's mouth). If it only nicks the skin, think of the germs entering your bloodstream. |
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"It's not the bullet that kills you; it's the hole" -- Laurie Anderson |
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//The best I could think of was cheap parking near the building.// |
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That was what got my vote. |
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Hmm. I hadn't fully considered non-coins. Pricing would have to be determined for other objects, probably based on damage, liability, etc. I would look forward to the annual bowling ball day, although I think I'd want to show up early. I wouldn't want to try to run into the building after things got started. |
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feefall
Can I drop a roll of pennies on you? it's only a handful! There's more than just velocity to consider. One penny would bounce off your head a roll might kill you. |
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Same with a bowling ball. Your point was...? |
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Sure you can drop a roll of pennies on me, if you take it out of the wrapper first. $0.50 worth of still-rolled pennies probably could kill someone. |
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You have a 'nonfunctioning-copy-machine Day' by chance? |
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Save yourself the money. Throw a penny in the air and watch it land. Pretty exciting isn't it? Take a souvenir picture too, if you want. |
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Didn't David Letterman already exploit this Idea to no end? |
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And by the way, a watermelon or a frozen turkey exploding on impact are two of the funniest sights you may ever come across in your lifetime |
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I bet that whale that exploded in downtown Tainan, Taiwan would make the top 3 as well [Wordup]! (Linky) |
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going back to the idea of breakable targets, why don't we all bring pictures and objects of things we would like to smash. distasteful vases, pictures of ex-lovers, windows computers, etc. and smash those! i foresee hours of endless funa nd amusment. |
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Having ridden through a hailstorm on a motorcycle wearing an open faced crashe helmet, I can agree that whilst they may not kill, they smart some. As an added bonus, your face turns a wonderfully dappled red/white combo.
With respect to the subject matter, whilst I can see that the shape of a penny does not lend itself to acheiving a high terminal velocity, I'd not like one to land edge on on my noggin, even at a 'mere' 70 mph. perhaps you could replace the penny dispenser with a water balloon dispenser, it would add a frisson of excitement to the daily commute past the ESB - and for the dispensee - they joy of a direct hit would be hard to beat |
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Can I spend more and drop burning balls of acetone? the fireballs would completly disapear before hitting the ground but not before creating a pretty fire-waterfall effect. |
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You people need more to do. |
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According to Dennis Thompson (dthompson@lerc.nasa.gov), safety testing at NASA's Zero Gravity Research Center in Cleveland concluded that coins falling from a height of 510' in air achieve a terminal velocity that is too low to seriously injure a person it strikes, much less bury itself in concrete. |
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They should place lifelike dummies filled with red goo on the ground, so they explode on the onlookers when hit by pennies. |
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We've established that the penny couldn't kill someone, but I bet it still could cause injury or property damage. Suppose it hit a person in the eye who was looking up, or landed right on the windshield of a car. |
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I would think you'd need an enclosed chute for the penny to fall in, it could be attached to side of the building. This would actually open up other revenue streams, for instance charge someone extra to put an item of their choice at the bottom of the chute to be hit by a falling penny, etc. |
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I'll bet if I bent a copper penny in half, it would improve the aerodynamic characterstics quite a bit--maybe enough to overcome the flutter problem. Hmmm... |
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A penny dropping off a skyscraper isn't exactly an amazing sight. It'll hit the ground at approximately 25 mph, if it even makes it to the ground. Updrafts send many pennies to the roofs of other buildings, or to setback roofs on the same building. |
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The next time I go to Chicago, remind me to snoop around on the roofs for some change. |
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There should be a wishing well on the landing area. If your penny drops into 1 metre diameter wishing well you can consider yourself lucky. And you are granted a wish. Penny for your thoughts? |
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Theres a slight problem with winds but I would put my 51 cents up just for the heck of it. I personally would love a building to build a drop garden which has an assortment of drops daily. Such as paintballs, frozen poultry, bowlingballs, various flaming objects, oboes, and cable modems. |
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So this is a wishing cliff? |
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Oh, I couldn't resist the challenge. |
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As far as I can tell, the terminal velocity works out around 65m/s, or 139 mph. That's for the coin falling edge-on, for which the Cd comes out at about 0.5. |
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Nope, I wouldn't stand under that. |
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in order to fall edge first, one area of the edge will have to be significantly heavier than the trailing, as it is a coin will spin. look at it this way, if u try really hard to stand a penny on its edge it may stand up, but you cannot stand a penny on the air pressure of its terminal velocity. 139mph wind will quickly turn a penny on its side starting the spin. the terminal velocity of 25-70 exactly that - terminal velocity. |
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Put the cheap parking on top of the
skyscraper, each time someone deposits a
penny for a ticket the car which has been
there the longest gets launched off the
top onto the ground below. |
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You never run out of spaces and you get
a free tourist attraction. |
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Letterman always fenced the area off- boring! Old school! |
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Instead, make it $5.00 to drop a penny, but let people throw them. Then, use $4.50 for the insurance, and still get .50 for maintenance. And, sell photos of the impact (especially on unsuspecting pedestrians, taxis, hot dog stands) to boot. |
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//in order to fall edge first, one area of the edge will have to be significantly heavier than the trailing, as it is a coin will spin.// |
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Unless you span it like a wheel as you threw it, of course. I don't know how much spin you'd need to resist tumbling, but it's pretty easy to add 'flat' spin to something as you throw it - skimming stones on water works because of this. |
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I'm guessing friction will stop the thing spinning fairly quickly. But I have no science to prove it. |
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When I first saw this I figured that the penny would be encased in some sort of tube going the full height of the building so that there would be no wind drag (other than the air in the tube) |
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[Jscotty] Now there's an idea. Except evacuate* the tube. That'll send up some serious sparks when they hit the pavement**. |
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* Why isn't this word spelled "evacuuate"? |
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**pavement section inside of evacuated chamber at bottom, along with (vacuum-space appropriate) objects you'd like to destroy. |
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Put it in a vaccuum chamber with a soft target and a video camera at bottom. |
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