boon racoon Posted June 23, 2005 Report Share Posted June 23, 2005 (edited) no..only joking. we had that question years ago. think about THIS if you put a slinky spring at the top of an esculator which was travelling upwards, and pushed the slinky down...what would happen?! what if the esculator was going the same speed as the slinky? any ideas? cos...i dunno (Y) Edited June 23, 2005 by the boon Quote Link to comment Share on other sites More sharing options...
JT! Posted June 23, 2005 Report Share Posted June 23, 2005 no..only joking. we has that question years ago. think about THIS if you put a slinky spring at the top of an esculator which was travelling upwards, and pushed the slinky down...what would happen?! what if the esculator was going the same speed as the slinky? any ideas? cos...i dunno (Y) ← If the speeds were correct, yes, it would go on for ever and ever like the duracell bunnys. No a fly cannot stop a train, but, the fly does stop. Quote Link to comment Share on other sites More sharing options...
MrMonkey Posted June 23, 2005 Report Share Posted June 23, 2005 no..only joking. we has that question years ago. think about THIS if you put a slinky spring at the top of an esculator which was travelling upwards, and pushed the slinky down...what would happen?! what if the esculator was going the same speed as the slinky? any ideas? cos...i dunno (Y) ← It would continue to move forward, but not move if you get me. Like it'll do it's cashink cashink cashink thing but not actually go further down. And a fly could stop a train. If it was a giant fly. Quote Link to comment Share on other sites More sharing options...
Sameer Posted June 23, 2005 Report Share Posted June 23, 2005 If a fly was buzzing around in the drivers area and sat down on the brake pedal (or whatever trains use), the driver would stamp on the pedal to kill the fly, thus stopping the train. So, a fly can stop a train. Albeit a dead one. Quote Link to comment Share on other sites More sharing options...
Janson Posted June 23, 2005 Report Share Posted June 23, 2005 if the fly and train were indestructable and the fly travelled at a very high speed and collided head-on, yes. but in reality, not really. Quote Link to comment Share on other sites More sharing options...
Phatmike Posted June 23, 2005 Report Share Posted June 23, 2005 Momentum (kgm/s) = mass (kg) x velocity (m/s) yeh? So if the train's going really slowly, say 10 m/s (same as a sprinter), and weighs what, 10 (metric) tonnes (= 10,000kg), so it's momentum = 10,000 * 10 = 1,000,000 kgm/s. And a fly weighs what 1g (=0.001kg)? Under the "conservation of momentum", ignoring air resistance etc, this means that if a fly which had a mass of 1g was going at 1,000,000,000 m/s (2,236,000,000 miles an hour), then it could stop a train which had a mass of 10 tonnes and was going at 10 m/s (22.36mph) Man I'm bored. (Y) Quote Link to comment Share on other sites More sharing options...
downhill_rob2@hotmail.com Posted June 23, 2005 Report Share Posted June 23, 2005 Momentum (kgm/s) = mass (kg) x velocity (m/s) yeh? So if the train's going really slowly, say 10 m/s (same as a sprinter), and weighs what, 10 (metric) tonnes (= 10,000kg), so it's momentum = 10,000 * 10 = 1,000,000 kgm/s. And a fly weighs what 1g (=0.001kg)? Under the "conservation of momentum", ignoring air resistance etc, this means that if a fly which had a mass of 1g was going at 1,000,000,000 m/s (2,236,000,000 miles an hour), then it could stop a train which had a mass of 10 tonnes and was going at 10 m/s (22.36mph) Man I'm bored. (Y) ← HAHA, thats quite true! lol BUT!!! I know how it can really stop an electric train... it may fly into the main electric wire/cable, and then it might explode and the train will blow up, then eventually it will stop??? Quote Link to comment Share on other sites More sharing options...
quick_spider Posted June 23, 2005 Report Share Posted June 23, 2005 Momentum (kgm/s) = mass (kg) x velocity (m/s) yeh? So if the train's going really slowly, say 10 m/s (same as a sprinter), and weighs what, 10 (metric) tonnes (= 10,000kg), so it's momentum = 10,000 * 10 = 1,000,000 kgm/s. And a fly weighs what 1g (=0.001kg)? Under the "conservation of momentum", ignoring air resistance etc, this means that if a fly which had a mass of 1g was going at 1,000,000,000 m/s (2,236,000,000 miles an hour), then it could stop a train which had a mass of 10 tonnes and was going at 10 m/s (22.36mph) Man I'm bored. (Y) ← Sadly that's about 3x the speed of light... Special Relativity anyone? Jon Quote Link to comment Share on other sites More sharing options...
Brian Bleech Posted June 23, 2005 Report Share Posted June 23, 2005 wouldn't the friction of the slinky and the slinky/esculator contact points eventually cause the to deccelerate and wouldn't be able to 'slink' downwards fast enough to counteract the upwards movement of the esculator. though this doesn't matter if you assume the slinky is frictionless and the slinky/esculator has a co-effiecent of zero mike Quote Link to comment Share on other sites More sharing options...
Brian Bleech Posted June 23, 2005 Report Share Posted June 23, 2005 if was a fly on tracks then the train would have to stop for it, because it might derail the train Quote Link to comment Share on other sites More sharing options...
TheChai Posted June 23, 2005 Report Share Posted June 23, 2005 or it might not see day light again Quote Link to comment Share on other sites More sharing options...
ScotchDave Posted June 23, 2005 Report Share Posted June 23, 2005 Momentum (kgm/s) = mass (kg) x velocity (m/s) yeh? So if the train's going really slowly, say 10 m/s (same as a sprinter), and weighs what, 10 (metric) tonnes (= 10,000kg), so it's momentum = 10,000 * 10 = 1,000,000 kgm/s. And a fly weighs what 1g (=0.001kg)? Under the "conservation of momentum", ignoring air resistance etc, this means that if a fly which had a mass of 1g was going at 1,000,000,000 m/s (2,236,000,000 miles an hour), then it could stop a train which had a mass of 10 tonnes and was going at 10 m/s (22.36mph) Man I'm bored. (Y) ← Mike, you forgot to allow for the increase in mass of the fly. Let's see, a train has that has relativistic mass 10 tonnes and is traveling at say 100ms^1. Then it's momentum is 10,000,000 kgms^-1. So the fly needs a momentum of 10,000,000 kgms^-1. Now somethings mass at speed is given by m=m0/(1-(v/c)^2)^1/2 We now have 2 unknown's, relativistic mass and speed, I'm too lazy to finish it, one of you can. :P :) Quote Link to comment Share on other sites More sharing options...
Janson Posted June 23, 2005 Report Share Posted June 23, 2005 point is, the fly must be either obese or on drugs to stop the train. Quote Link to comment Share on other sites More sharing options...
tipsy Jock Posted June 23, 2005 Report Share Posted June 23, 2005 if the fly and train were indestructable and the fly travelled at a very high speed and collided head-on, yes. but in reality, not really. ← *cough* trains indestructable too :P Maybe they would stop each other lol does that count? (Y) Pete Quote Link to comment Share on other sites More sharing options...
MrMonkey Posted June 23, 2005 Report Share Posted June 23, 2005 *cough* trains indestructable too :P Maybe they would stop each other lol does that count? (Y) Pete ← The train would have to be indestructable or else the fly would just cut a chonging hole in it. Quote Link to comment Share on other sites More sharing options...
Tomm Posted June 23, 2005 Report Share Posted June 23, 2005 point is, the fly must be either obese or on drugs to stop the train. ← BUT they fly cannot simply be going forwards once instant, and then the next be going backwards. It must stop before it changes direction. So if it stops, the train stops (Y) Quote Link to comment Share on other sites More sharing options...
JT! Posted June 23, 2005 Report Share Posted June 23, 2005 BUT they fly cannot simply be going forwards once instant, and then the next be going backwards. It must stop before it changes direction. So if it stops, the train stops (Y) ← But the train can't stop, that would mean it would stop and start without anyone knowing. There for going from 0mph to 50 mph instantly, which is impossible. Quote Link to comment Share on other sites More sharing options...
Royaltrials Posted June 23, 2005 Report Share Posted June 23, 2005 But the train can't stop, that would mean it would stop and start without anyone knowing. There for going from 0mph to 50 mph instantly, which is impossible. ← The fly does stop the train, we concurred this matter on the trialskings forum about 23 years ago. Another question... can a candle burn in space? Give reasons. There is oxygen in the space shuttle. Quote Link to comment Share on other sites More sharing options...
Bionic Balls Posted June 23, 2005 Report Share Posted June 23, 2005 well mike... i didn't see it like that :) I used the formula: (conservation of momentum) m1u1 + m2u2= m1v1 + m2v2 lets say m1 is the train (10,000kg) and m2 is the fly (0.001kg) as you said..the train is moving at 10m/s using the COM: 10,000(10) + 0.001(u2) = 10,000(v1) + 0.001(v2) you see...we don't know how fast the fly will "bounce" off the train yet...but, we'll say that the train stops...therefore: 100,000+ 0.001u2= 0.001v2 To work out how fast the fly will bounce at...i'll use newton's coefficient of restitution: e= speed of separation/ speed of approach now lets assume e is between o and 1 (reasonable :P ).... therefore e= v2/10-u2 so v2= 10e - eu2 We know that 100,000 + 0.001u2= 0.001v2 so 100,000 + 0.001u2= 0.001(10e- eu2) 100,000 + 0.001u2= 0.01e - 0.001eu2 lets say e=1 (now) therefore 0.001u2= 0.01-0.001u2 - 100,000 u2= -49999995 m/s If e=0 u2= -100000000 m/s don't worry that they are -ve (they are moving in the opposite dir. to the train...) if v2= 10e - eu2 v2= 50000005 = 5.0 x 10^7m/s I don't know who is right..i'v done some assuming....and typing it out gets really confusing :P my speed is possible....with a big gun (Y) anyways...anyone else doing mechanics 2 tomorrow? adam Quote Link to comment Share on other sites More sharing options...
Royaltrials Posted June 23, 2005 Report Share Posted June 23, 2005 now lets assume e is between o and 1 (reasonable (Y) ).... anyways...anyone else doing mechanics 2 tomorrow? adam ← The coefficient of restitution is always between 0 and 1. I don't think it would be much bigger than 0. How high would a fly bounce off a glass surface? Simplifying things greatly: If the coefficient is 1 then the object bounces back up to the height from which it was dropped. M2 is piss, but hope it goes well. Quote Link to comment Share on other sites More sharing options...
Bionic Balls Posted June 23, 2005 Report Share Posted June 23, 2005 exactly.... (Y) m2 is not piss...i can't bring myself to say that yet. adam Quote Link to comment Share on other sites More sharing options...
Davetrials Posted June 23, 2005 Report Share Posted June 23, 2005 OMFG! most confusing topic EVER!!!!!! (Y) Quote Link to comment Share on other sites More sharing options...
Simon Posted June 23, 2005 Report Share Posted June 23, 2005 OMFG! most confusing topic EVER!!!!!! (Y) ← Hahaha. Matt didn't even ask if a fly could stop a train, that was just to get people into the topic. :P Good stuff. I bet Matt is like; "What the duck? :) ". Quote Link to comment Share on other sites More sharing options...
JT! Posted June 23, 2005 Report Share Posted June 23, 2005 The fly does stop the train, we concurred this matter on the trialskings forum about 23 years ago. ← No, it can't. Quote Link to comment Share on other sites More sharing options...
yoyoyo Posted June 23, 2005 Report Share Posted June 23, 2005 i get how the fly stops but not the train Quote Link to comment Share on other sites More sharing options...
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