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#12
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Bicycle riddle
On 5/27/2017 12:21 AM, Frank Krygowski wrote:
On Friday, May 26, 2017 at 11:48:13 PM UTC-4, Jeff Liebermann wrote: On Fri, 26 May 2017 20:36:39 -0700 (PDT), Frank Krygowski wrote: Bicycle riddle: http://www.popularmechanics.com/scie...icycle-killer/ - Frank Krygowski When you're done with that bicycle riddle, try this bicycle mechanical problem: http://www.popularmechanics.com/science/math/a26070/riddle-of-the-week-24/ (I guessed wrong, as usual). I got it, but by a very different mental process than what they used. I'll hold off discussing until others have had a chance to work on it. - Frank Krygowski So little interest in the riddle that was actually technical! -- - Frank Krygowski |
#13
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Bicycle riddle
Frank Krygowski wrote:
On 5/27/2017 12:21 AM, Frank Krygowski wrote: On Friday, May 26, 2017 at 11:48:13 PM UTC-4, Jeff Liebermann wrote: On Fri, 26 May 2017 20:36:39 -0700 (PDT), Frank Krygowski wrote: Bicycle riddle: http://www.popularmechanics.com/scie...icycle-killer/ - Frank Krygowski When you're done with that bicycle riddle, try this bicycle mechanical problem: http://www.popularmechanics.com/science/math/a26070/riddle-of-the-week-24/ (I guessed wrong, as usual). I got it, but by a very different mental process than what they used. I'll hold off discussing until others have had a chance to work on it. - Frank Krygowski So little interest in the riddle that was actually technical! It was relatively obvious (by virtue of the fact that it was posed as a riddle, there had to be some non-intuitiveness to the answer) and I deduced the right answer. There just wasn't much left to talk about afterwards. |
#14
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Bicycle riddle
On Sun, 28 May 2017 14:07:40 -0400, Frank Krygowski
wrote: Actually, 53 bicycles in the room (as stated in the original riddle) would mean something like 26.5 cards. Each "Bicycle" brand playing card shows two bicycles, not just one. Yep, although the alleged bicycle appears rather painful to ride without a saddle and is missing the pedals: https://cdn3.volusion.com/artgw.hyvvw/v/vspfiles/photos/CB00741-3.jpg At least, that's what I assume, based on the name. On the cards, they're illustrated as a head on view, ridden by angels. If not for the name, one might suppose the angels are riding unicycles. I would guess(tm) that a unicycle could be considered half of a bicycle, thus returning the total count to 53. At one time, Bicycle playing cards had recognizeable bicycles on the back: http://www.bicyclecards.com/wp-content/uploads/2015/06/18921.jpg -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#15
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Bicycle riddle
On 5/28/2017 2:58 PM, Ralph Barone wrote:
Frank Krygowski wrote: On 5/27/2017 12:21 AM, Frank Krygowski wrote: On Friday, May 26, 2017 at 11:48:13 PM UTC-4, Jeff Liebermann wrote: On Fri, 26 May 2017 20:36:39 -0700 (PDT), Frank Krygowski wrote: Bicycle riddle: http://www.popularmechanics.com/scie...icycle-killer/ - Frank Krygowski When you're done with that bicycle riddle, try this bicycle mechanical problem: http://www.popularmechanics.com/science/math/a26070/riddle-of-the-week-24/ (I guessed wrong, as usual). I got it, but by a very different mental process than what they used. I'll hold off discussing until others have had a chance to work on it. - Frank Krygowski So little interest in the riddle that was actually technical! It was relatively obvious (by virtue of the fact that it was posed as a riddle, there had to be some non-intuitiveness to the answer) and I deduced the right answer. There just wasn't much left to talk about afterwards. Just curious: How did you deduce the right answer? I can see one very detailed way, requiring some simple math, and one sort of shortcut way, no numbers required. I used the shortcut. -- - Frank Krygowski |
#16
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Bicycle riddle
On Sunday, May 28, 2017 at 2:56:44 PM UTC-7, Frank Krygowski wrote:
On 5/28/2017 2:58 PM, Ralph Barone wrote: Frank Krygowski wrote: On 5/27/2017 12:21 AM, Frank Krygowski wrote: On Friday, May 26, 2017 at 11:48:13 PM UTC-4, Jeff Liebermann wrote: On Fri, 26 May 2017 20:36:39 -0700 (PDT), Frank Krygowski wrote: Bicycle riddle: http://www.popularmechanics.com/scie...icycle-killer/ - Frank Krygowski When you're done with that bicycle riddle, try this bicycle mechanical problem: http://www.popularmechanics.com/science/math/a26070/riddle-of-the-week-24/ (I guessed wrong, as usual). I got it, but by a very different mental process than what they used. I'll hold off discussing until others have had a chance to work on it. - Frank Krygowski So little interest in the riddle that was actually technical! It was relatively obvious (by virtue of the fact that it was posed as a riddle, there had to be some non-intuitiveness to the answer) and I deduced the right answer. There just wasn't much left to talk about afterwards. Just curious: How did you deduce the right answer? I can see one very detailed way, requiring some simple math, and one sort of shortcut way, no numbers required. I used the shortcut. I haven't played any game requiring cards since I was a child. And the number 53 would not have occurred to me since only children that were a lot younger than me played with a deck of cards with a joker in it. So there was no way I could have deduced that. |
#17
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Bicycle riddle
Frank Krygowski wrote:
On 5/28/2017 2:58 PM, Ralph Barone wrote: Frank Krygowski wrote: On 5/27/2017 12:21 AM, Frank Krygowski wrote: On Friday, May 26, 2017 at 11:48:13 PM UTC-4, Jeff Liebermann wrote: On Fri, 26 May 2017 20:36:39 -0700 (PDT), Frank Krygowski wrote: Bicycle riddle: http://www.popularmechanics.com/scie...icycle-killer/ - Frank Krygowski When you're done with that bicycle riddle, try this bicycle mechanical problem: http://www.popularmechanics.com/science/math/a26070/riddle-of-the-week-24/ (I guessed wrong, as usual). I got it, but by a very different mental process than what they used. I'll hold off discussing until others have had a chance to work on it. - Frank Krygowski So little interest in the riddle that was actually technical! It was relatively obvious (by virtue of the fact that it was posed as a riddle, there had to be some non-intuitiveness to the answer) and I deduced the right answer. There just wasn't much left to talk about afterwards. Just curious: How did you deduce the right answer? I can see one very detailed way, requiring some simple math, and one sort of shortcut way, no numbers required. I used the shortcut. If you look at the system, the "gain" in torque from pedals to wheels is less than one (for almost all bikes), therefore the mechanical advantage is greater than one in the other direction. If you had locked the drivetrain and pulled on the pedal with a string, there would be equal and opposite forces on the pedal and the tire. Putting it all together, if you apply some force to the tire and an equal force to the pedal, the force applied to the tire will "win" and the bike will move forwards. |
#18
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Bicycle riddle
On 5/28/2017 7:55 PM, Ralph Barone wrote:
Frank Krygowski wrote: On 5/28/2017 2:58 PM, Ralph Barone wrote: Frank Krygowski wrote: On 5/27/2017 12:21 AM, Frank Krygowski wrote: On Friday, May 26, 2017 at 11:48:13 PM UTC-4, Jeff Liebermann wrote: On Fri, 26 May 2017 20:36:39 -0700 (PDT), Frank Krygowski wrote: Bicycle riddle: http://www.popularmechanics.com/scie...icycle-killer/ - Frank Krygowski When you're done with that bicycle riddle, try this bicycle mechanical problem: http://www.popularmechanics.com/science/math/a26070/riddle-of-the-week-24/ (I guessed wrong, as usual). I got it, but by a very different mental process than what they used. I'll hold off discussing until others have had a chance to work on it. - Frank Krygowski So little interest in the riddle that was actually technical! It was relatively obvious (by virtue of the fact that it was posed as a riddle, there had to be some non-intuitiveness to the answer) and I deduced the right answer. There just wasn't much left to talk about afterwards. Just curious: How did you deduce the right answer? I can see one very detailed way, requiring some simple math, and one sort of shortcut way, no numbers required. I used the shortcut. If you look at the system, the "gain" in torque from pedals to wheels is less than one (for almost all bikes), therefore the mechanical advantage is greater than one in the other direction. If you had locked the drivetrain and pulled on the pedal with a string, there would be equal and opposite forces on the pedal and the tire. Putting it all together, if you apply some force to the tire and an equal force to the pedal, the force applied to the tire will "win" and the bike will move forwards. Except you got it wrong! For the pedal position shown (crank vertical, string pulling horizontally backwards on the bottom pedal, and a bike with common gearing) the bike moves _backwards_ when the string tries to rotate the cranks in their normal direction. See http://www.popularmechanics.com/scie...f-the-week-24/ So the new question is: Why? Or if people want to get more mathematical, we could ask under what conditions would the bike move forward instead. -- - Frank Krygowski |
#19
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Bicycle riddle
Frank Krygowski wrote:
On 5/28/2017 7:55 PM, Ralph Barone wrote: Frank Krygowski wrote: On 5/28/2017 2:58 PM, Ralph Barone wrote: Frank Krygowski wrote: On 5/27/2017 12:21 AM, Frank Krygowski wrote: On Friday, May 26, 2017 at 11:48:13 PM UTC-4, Jeff Liebermann wrote: On Fri, 26 May 2017 20:36:39 -0700 (PDT), Frank Krygowski wrote: Bicycle riddle: http://www.popularmechanics.com/scie...icycle-killer/ - Frank Krygowski When you're done with that bicycle riddle, try this bicycle mechanical problem: http://www.popularmechanics.com/science/math/a26070/riddle-of-the-week-24/ (I guessed wrong, as usual). I got it, but by a very different mental process than what they used. I'll hold off discussing until others have had a chance to work on it. - Frank Krygowski So little interest in the riddle that was actually technical! It was relatively obvious (by virtue of the fact that it was posed as a riddle, there had to be some non-intuitiveness to the answer) and I deduced the right answer. There just wasn't much left to talk about afterwards. Just curious: How did you deduce the right answer? I can see one very detailed way, requiring some simple math, and one sort of shortcut way, no numbers required. I used the shortcut. If you look at the system, the "gain" in torque from pedals to wheels is less than one (for almost all bikes), therefore the mechanical advantage is greater than one in the other direction. If you had locked the drivetrain and pulled on the pedal with a string, there would be equal and opposite forces on the pedal and the tire. Putting it all together, if you apply some force to the tire and an equal force to the pedal, the force applied to the tire will "win" and the bike will move forwards. Except you got it wrong! For the pedal position shown (crank vertical, string pulling horizontally backwards on the bottom pedal, and a bike with common gearing) the bike moves _backwards_ when the string tries to rotate the cranks in their normal direction. See http://www.popularmechanics.com/scie...f-the-week-24/ So the new question is: Why? Or if people want to get more mathematical, we could ask under what conditions would the bike move forward instead. Yeah, that too... I actually did get it right, then botched it during the explanation (and you can choose to believe that it or not, as you see fit). I alluded to one possible situation where the bike would go forward, and that was ultra low geared bikes. If the combination of long cranks, small front chainring, large rear sprocket and small rear wheel combined to make the bike move less than 2•pi•crank length for each rotation of the crank, then the bike will move forwards (at first, at least). |
#20
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Bicycle riddle
On Sun, 28 May 2017 09:07:31 -0500,
AMuzi wrote: On 5/27/2017 4:06 PM, wrote: On Saturday, May 27, 2017 at 9:17:32 AM UTC-7, AMuzi wrote: On 5/27/2017 8:53 AM, wrote: On Friday, May 26, 2017 at 8:36:41 PM UTC-7, Frank Krygowski wrote: Bicycle riddle: http://www.popularmechanics.com/scie...icycle-killer/ Is there supposed to be something there other than a written question? click this, Tom: http://www.popularmechanics.com/scie...f-the-week-28/ When did people start playing poker with a joker in the deck? Never. In my experience, dealer opens a new deck with all participants watching, removes the joker and shuffles before dealing. I seem to recall that new decks typically have not one, but two jokers. -- Ted Heise Bloomington, IN, USA |
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