RMweb Premium Jeremy Cumberland Posted January 19 RMweb Premium Share Posted January 19 6 hours ago, billbedford said: There is no force involved, there is a local change in pressure as an aerofoil moves through a medium. The pressure is lowered above a wing and raised beneath. In effect, the atmosphere sucks the wing upwards. Birds might use the aerofoil effect when they are airborne, but most of them take off by flapping their wings. This looks like force to me. Clearly the overall mass of the lift and its contents doesn't change whatever the birds do, not unless some air gets forced out or sucked in. This doesn't necessarily mean that the force on the lift cable doesn't change, and you can imagine the extreme case of a jumping elephant. As the elephant jumps, it applies a force greater than its weight to the lift floor, which in turn is transmitted up to the cable. When the elephant becomes airborne, its weight is no longer being supported by the lift floor, and since elephants aren't like birds and able to manipulate the local air pressure to stay airborne, its weight isn't actually supported by anything. The tension in the lift cable decreases, and the elephant experiences a downwards acceleration. It's upwards speed rapidly decreases, turning into a downwards speed that rapidly increases, till thump! It hits the lift floor, giving a shock to the cable. How many jumping elephants were allowed in the lift? 3 Link to post Share on other sites More sharing options...
RMweb Gold The Johnster Posted January 19 RMweb Gold Share Posted January 19 On 18/01/2024 at 13:38, 30801 said: This man has found a workaround. I like the way it looks as if the horse is pedalling with it's front legs! 1 Link to post Share on other sites More sharing options...
RMweb Gold The Johnster Posted January 19 RMweb Gold Share Posted January 19 6 minutes ago, Jeremy Cumberland said: Birds might use the aerofoil effect when they are airborne, but most of them take off by flapping their wings. This looks like force to me. Clearly the overall mass of the lift and its contents doesn't change whatever the birds do, not unless some air gets forced out or sucked in. This doesn't necessarily mean that the force on the lift cable doesn't change, and you can imagine the extreme case of a jumping elephant. As the elephant jumps, it applies a force greater than its weight to the lift floor, which in turn is transmitted up to the cable. When the elephant becomes airborne, its weight is no longer being supported by the lift floor, and since elephants aren't like birds and able to manipulate the local air pressure to stay airborne, its weight isn't actually supported by anything. The tension in the lift cable decreases, and the elephant experiences a downwards acceleration. It's upwards speed rapidly decreases, turning into a downwards speed that rapidly increases, till thump! It hits the lift floor, giving a shock to the cable. How many jumping elephants were allowed in the lift? But in order to become temporarily airborne, Jumbo must initially exert exess downward pressure on the lift floor using his muscles to achieve space between the hatstand bits and the floor. This will increase tension on the cable, which will be removed when he's off the floor, and the lift's downward moment will reduce his impact when he lands again. Hence his average weight, plus that of the lift cage, will remain constant over time. If the lift is free-falling, he might be advised to jump repeatedly in the hope of being in upward motion when it hits the ground, but will probably be taken out by violent contact with the roof... 2 Link to post Share on other sites More sharing options...
RMweb Gold Metr0Land Posted January 19 RMweb Gold Share Posted January 19 5 hours ago, 25kV said: The principle has been tested with flying insects in a sealed jar on a sensitive scale. The weight of the insect is borne by the air in the jar while they are flying, and thus the total weight on the scale remains the same. Thus it follows that airborne grouse would still "weigh" the same inside the lift. Schroedinger's ants? 4 Link to post Share on other sites More sharing options...
RMweb Premium PhilJ W Posted January 19 RMweb Premium Share Posted January 19 (edited) 1 hour ago, Sidecar Racer said: But if the grouse isn't in contact with any part the lift surface then surely it can't be adding any weight . But what if they all decided to land at the same time? Edited January 19 by PhilJ W 1 Link to post Share on other sites More sharing options...
MartinRS Posted January 19 Share Posted January 19 2 hours ago, Jeremy Cumberland said: Birds might use the aerofoil effect when they are airborne, but most of them take off by flapping their wings. This looks like force to me. Clearly the overall mass of the lift and its contents doesn't change whatever the birds do, not unless some air gets forced out or sucked in. This doesn't necessarily mean that the force on the lift cable doesn't change, and you can imagine the extreme case of a jumping elephant. As the elephant jumps, it applies a force greater than its weight to the lift floor, which in turn is transmitted up to the cable. When the elephant becomes airborne, its weight is no longer being supported by the lift floor, and since elephants aren't like birds and able to manipulate the local air pressure to stay airborne, its weight isn't actually supported by anything. The tension in the lift cable decreases, and the elephant experiences a downwards acceleration. It's upwards speed rapidly decreases, turning into a downwards speed that rapidly increases, till thump! It hits the lift floor, giving a shock to the cable. How many jumping elephants were allowed in the lift? There's one fatal flaw in your argument. Elephants can't jump! 3 Link to post Share on other sites More sharing options...
RMweb Premium Ian Morgan Posted January 19 RMweb Premium Share Posted January 19 3 1 Link to post Share on other sites More sharing options...
MartinRS Posted January 19 Share Posted January 19 (edited) 1 hour ago, Metr0Land said: Schroedinger's ants? I didn't know that such a a beast existed. I have seen Schroedinger' dead sheep though. It's out there on the moors just waiting for the unwary traveller! Just venture out into the wilds and it's sure to get you! All you have to do to summon this diabolical creature is to take a sip from a clear mountain stream. Only when the cool refreshing water has passed your throat will you get to see if it's upstream or downstream of your location! Edited January 19 by MartinRS typo 1 4 Link to post Share on other sites More sharing options...
Hroth Posted January 19 Share Posted January 19 24 minutes ago, MartinRS said: There's one fatal flaw in your argument. Elephants can't jump! But they do walk on tiptoe! As for Schrodingers Dead Sheep, apparently its ok if its more than 10ft upstream. Not that I'd want to risk it.... 1 Link to post Share on other sites More sharing options...
Steamport Southport Posted January 19 Share Posted January 19 35 minutes ago, MartinRS said: There's one fatal flaw in your argument. Elephants can't jump! Neither can white men according to Wesley Snipes. We still manage to get in a lift though! Has anyone seen how much space a few pheasants take up in a kitchen? Similar size things. It's more the size than the weight. 1 Link to post Share on other sites More sharing options...
RMweb Gold The Johnster Posted January 19 RMweb Gold Share Posted January 19 38 minutes ago, Hroth said: But they do walk on tiptoe! As for Schrodingers Dead Sheep, apparently its ok if its more than 10ft upstream. Not that I'd want to risk it.... Not sure you can apply Shroedinger to a dead sheep, or a live one. It has to be a sheep (or a cat) whose status vis a vis remaining amongst the living is unknown, as circumstances demand that you cannot ascertain this aspect of it's status. Hence it can be regarded as both living and dead at the same time. Of course, except for the nanosecond that it is actually transitioning from a living state to a dead one, it actually is either living or dead in fact, but since you don't know, but you know it exists in one of those states, you must proceed on the assumption that it is simultaneously alive and dead. I contend that this does not apply to a dead sheep on a mountain upstream of the point that you are drinking from, because you are presumably at that point unaware of that sheep's existence. You know, of course, of the existence of sheep on the mountain in general, but not that specific sheep. When you become aware of it's existence, it becomes obvious that it has shuffled off it's mortal coil (which I believe is a component of a 1930s radio) and that therefore Schroedinger cannot be applied to it, neither can he be applied to other sheeps within your field of vision which are wandering around and bleating at you. If it were not so, I would be able to consider the entire world population of sheeps to be Schroedinger's sheep, both alive and dead at the same time, because I cannot see any of them from my living room sofa upon which I am typing this rubbish, and that would obviously be daft! OTOH, it might be considered daft to consider sheeps, or cats, in terms of illustrating hypothesis in the field of particle physics. I don't really know, but since Schroedinger knew more than me about this sort of thing I'm happy to take his word for it, and to recommend that you do as well... 3 2 Link to post Share on other sites More sharing options...
MartinRS Posted January 19 Share Posted January 19 5 hours ago, Deeps said: More specifically, are they African or European? (another Monty Python scenario) Scottish-African surely and bred for the the hunting pleasure of Idi Amin Dada, the last King of Scotland. I've just come down from the Isle of Skye I'm not very big and I'm awful shy... No! Stop! Stop! Sorry, whenever I see the word Scotland I have an urge to burst into that well-known national anthem! Link to post Share on other sites More sharing options...
Popular Post Steamport Southport Posted January 19 Popular Post Share Posted January 19 1 hour ago, The Johnster said: Not sure you can apply Shroedinger to a dead sheep, or a live one. It has to be a sheep (or a cat) whose status vis a vis remaining amongst the living is unknown, as circumstances demand that you cannot ascertain this aspect of it's status. Hence it can be regarded as both living and dead at the same time. Of course, except for the nanosecond that it is actually transitioning from a living state to a dead one, it actually is either living or dead in fact, but since you don't know, but you know it exists in one of those states, you must proceed on the assumption that it is simultaneously alive and dead. I contend that this does not apply to a dead sheep on a mountain upstream of the point that you are drinking from, because you are presumably at that point unaware of that sheep's existence. You know, of course, of the existence of sheep on the mountain in general, but not that specific sheep. When you become aware of it's existence, it becomes obvious that it has shuffled off it's mortal coil (which I believe is a component of a 1930s radio) and that therefore Schroedinger cannot be applied to it, neither can he be applied to other sheeps within your field of vision which are wandering around and bleating at you. If it were not so, I would be able to consider the entire world population of sheeps to be Schroedinger's sheep, both alive and dead at the same time, because I cannot see any of them from my living room sofa upon which I am typing this rubbish, and that would obviously be daft! OTOH, it might be considered daft to consider sheeps, or cats, in terms of illustrating hypothesis in the field of particle physics. I don't really know, but since Schroedinger knew more than me about this sort of thing I'm happy to take his word for it, and to recommend that you do as well... 6 1 13 Link to post Share on other sites More sharing options...
RMweb Premium Jeremy Cumberland Posted January 20 RMweb Premium Share Posted January 20 9 hours ago, Ian Morgan said: I am a little disappointed that these types of program ignore other observations that don't support their argument. Since the question of the truck crossing a bridge involved a steady state, this might be reasonable enough, but it risks creating as false an understanding as the truck driver had. Rather than ignore what they called noise, this does in fact show that the contents of the truck (or lift) can make short-term changes to its weight. In the video, the most striking example is when the helicopter operator makes rather a heavy landing. Look closely at the plot. The first movement is that the rig becomes lighter as the helicopter loses lift. Then the rig becomes heavier as helicopter hits the floor. The wobbles after that, with decreasing amplitude, are just ordinary elastic effects that you get in any mechanical system, similar to the vibrations after hitting a gong. My jumping elephant (and @MartinRS - how could you be so cruel shattering my dreams like that? I so wanted to live in a world where there were jumping elephants!) was chosen specifically because elephants can't fly (sorry, Dumbo), so the steady state of the birds beating their wings to create lift and counteract gravity doesn't exist. If the elephant could jump high enough, so the elastic vibrations from taking off die out before it lands, the plot would look something like this: ---/\____/\---- 2 Link to post Share on other sites More sharing options...
durham light infantry Posted January 20 Share Posted January 20 15 hours ago, MartinRS said: There's one fatal flaw in your argument. Elephants can't jump! Back to Schrodinger again. Just because nobody has seen them jump, doesn't mean that they can't. 1 Link to post Share on other sites More sharing options...
pH Posted January 20 Share Posted January 20 1 hour ago, durham light infantry said: Back to Schrodinger again. Just because nobody has seen them jump, doesn't mean that they can't. But wouldn’t there be reports of earth tremors in jungle areas? 2 Link to post Share on other sites More sharing options...
Steamport Southport Posted January 20 Share Posted January 20 49 minutes ago, pH said: But wouldn’t there be reports of earth tremors in jungle areas? There are though! https://en.wikipedia.org/wiki/List_of_earthquakes_in_India 2 Link to post Share on other sites More sharing options...
Hroth Posted January 20 Share Posted January 20 (edited) 18 hours ago, The Johnster said: Not sure you can apply Shroedinger to a dead sheep, or a live one. It has to be a sheep (or a cat) whose status vis a vis remaining amongst the living is unknown, as circumstances demand that you cannot ascertain this aspect of it's status. Hence it can be regarded as both living and dead at the same time. Of course, except for the nanosecond that it is actually transitioning from a living state to a dead one, it actually is either living or dead in fact, but since you don't know, but you know it exists in one of those states, you must proceed on the assumption that it is simultaneously alive and dead. I contend that this does not apply to a dead sheep on a mountain upstream of the point that you are drinking from, because you are presumably at that point unaware of that sheep's existence. You know, of course, of the existence of sheep on the mountain in general, but not that specific sheep. When you become aware of it's existence, it becomes obvious that it has shuffled off it's mortal coil (which I believe is a component of a 1930s radio) and that therefore Schroedinger cannot be applied to it, neither can he be applied to other sheeps within your field of vision which are wandering around and bleating at you. If it were not so, I would be able to consider the entire world population of sheeps to be Schroedinger's sheep, both alive and dead at the same time, because I cannot see any of them from my living room sofa upon which I am typing this rubbish, and that would obviously be daft! OTOH, it might be considered daft to consider sheeps, or cats, in terms of illustrating hypothesis in the field of particle physics. I don't really know, but since Schroedinger knew more than me about this sort of thing I'm happy to take his word for it, and to recommend that you do as well... Thanks for the dissertation on the concept of Shrodingers Dead Sheep, but it should have been directed at @MartinRS who introduced the subject! 19 hours ago, MartinRS said: I didn't know that such a a beast existed. I have seen Schroedinger' dead sheep though. It's out there on the moors just waiting for the unwary traveller! Just venture out into the wilds and it's sure to get you! All you have to do to summon this diabolical creature is to take a sip from a clear mountain stream. Only when the cool refreshing water has passed your throat will you get to see if it's upstream or downstream of your location! I just supplied a postulated safe drinking distance... Edited January 20 by Hroth spelin 1 Link to post Share on other sites More sharing options...
RMweb Premium Compound2632 Posted January 20 RMweb Premium Share Posted January 20 (edited) 2 hours ago, Hroth said: I just supplied a postulated safe drinking distance... Doesn't that belong in the dodgy driving driving standards thread? Edited January 20 by Compound2632 2 Link to post Share on other sites More sharing options...
RMweb Premium dale159 Posted January 21 RMweb Premium Share Posted January 21 https://www.google.co.uk/maps/@53.3946123,-2.7926641,3a,30y,104.5h,89.7t/data=!3m7!1e1!3m5!1swDPpWO_T-yhqpLud2Bt4kw!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3DwDPpWO_T-yhqpLud2Bt4kw%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D337.30588%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192?hl=en&authuser=0&entry=ttu 40 or 50mph? https://www.google.co.uk/maps/@53.3855689,-2.6920149,3a,37.5y,101.34h,88.62t/data=!3m6!1e1!3m4!1saCY-wpx_kfkTPpRYD7jRUQ!2e0!7i16384!8i8192?hl=en&authuser=0&entry=ttu 15 foot width restriction? Dale 1 4 Link to post Share on other sites More sharing options...
jcredfer Posted January 21 Share Posted January 21 5 hours ago, dale159 said: ......... https://www.google.co.uk/maps/@53.3855689,-2.6920149,3a,37.5y,101.34h,88.62t/data=!3m6!1e1!3m4!1saCY-wpx_kfkTPpRYD7jRUQ!2e0!7i16384!8i8192?hl=en&authuser=0&entry=ttu 15 foot width restriction? Dale Two 8ft lorries would be in trouble if travelling towards each other..... Come to think of it, a 6ft Merc might find it a bit tricky ensuring there was sufficient room to spare, before committing the paintwork... Oooh, the thought of it..... 🫠 Julian 1 Link to post Share on other sites More sharing options...
RMweb Premium Ian Morgan Posted January 21 RMweb Premium Share Posted January 21 'Drive' up to the bridge in Streetview, and the sign attached to it is 15 ft height restriction. 2 1 Link to post Share on other sites More sharing options...
RMweb Gold martin_wynne Posted January 21 RMweb Gold Share Posted January 21 (edited) 13 minutes ago, Ian Morgan said: 'Drive' up to the bridge in Streetview, and the sign attached to it is 15 ft height restriction. Or simply swap to an older date on the original Streetview: https://maps.app.goo.gl/4p6H4CwhLq6C1dE36 Edited January 21 by martin_wynne 2 Link to post Share on other sites More sharing options...
jcredfer Posted January 21 Share Posted January 21 10 minutes ago, Ian Morgan said: 'Drive' up to the bridge in Streetview, and the sign attached to it is 15 ft height restriction. Brilliant, and it certainly doesn't look anything like a mere 15ft wide. J 1 1 Link to post Share on other sites More sharing options...
RMweb Premium Andy Kirkham Posted January 21 RMweb Premium Share Posted January 21 Glenairlie Bridge over the River Nith adjacent to the G&SW main line. 4 1 Link to post Share on other sites More sharing options...
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