bouncebounce crunch Posted October 16, 2016 Share Posted October 16, 2016 my chickens run fast and flap their wings but fail to get higher than the gate post. Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted October 16, 2016 Share Posted October 16, 2016 Posted by Simon Chaddock on 16/10/2016 14:35:09: Gary You missed my point. What happens if the car moved the belt backwards very fast indeed. At some point the force required to stop the plane moving backward would become significant and in the extreme would equal to its thrust. Only if the wheels were frictionless (both the bearings & rolling resistance) would the belt speed have absolutely no impact on the plane and it would take off normally - actually slightly better than normal! In the real world the take off will be 'impaired' to a degree proportional to belt speed. I agree that the friction force would increase as the speed increased, but the degree of take off impairment would be miniscule compared with the engine thrust. Note that the friction force applied by the cars wheel bearings would be of the same magnitude, but that's not the main factor that limits the car's top speed, is it? Edited By Gary Manuel on 16/10/2016 15:08:35 Quote Link to comment Share on other sites More sharing options...
ted hughes Posted October 16, 2016 Share Posted October 16, 2016 Posted by Dave Hopkin on 16/10/2016 12:10:02: Ok, lets try again I wear roller skates and stand on the conveyor belt there is a rope running up the length of the belt attached to something not on the belt. I hold the rope and start to pull myself along it allowing the roller skate wheels to rotate as they wish The belt speeds up in response to my movement as per the original question Now what is stopping me working my way up the rope hand over hand? Nothing at all..... The rope equates to the engine thrust acting on the surrounding air...... hence the belt will have no effect on take off which will occur normally It sounds plausible, but in actual fact you would be trying to pull against an infinite amount of pressure and it could not be done. Quote Link to comment Share on other sites More sharing options...
J D 8 Posted October 16, 2016 Share Posted October 16, 2016 Posted by bouncebounce crunch on 16/10/2016 14:54:27: my chickens run fast and flap their wings but fail to get higher than the gate post. Funny thing my chickens do the same,must be some law of nature at work. Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted October 16, 2016 Share Posted October 16, 2016 Posted by ted hughes on 16/10/2016 15:59:34: Posted by Dave Hopkin on 16/10/2016 12:10:02: Ok, lets try again I wear roller skates and stand on the conveyor belt there is a rope running up the length of the belt attached to something not on the belt. I hold the rope and start to pull myself along it allowing the roller skate wheels to rotate as they wish The belt speeds up in response to my movement as per the original question Now what is stopping me working my way up the rope hand over hand? Nothing at all..... The rope equates to the engine thrust acting on the surrounding air...... hence the belt will have no effect on take off which will occur normally It sounds plausible, but in actual fact you would be trying to pull against an infinite amount of pressure and it could not be done. And what "pressure" would that be? Energy cannot just appear miraculously so where is this force coming from so there must be a source of this "infinite pressure" ????? Quote Link to comment Share on other sites More sharing options...
J D 8 Posted October 16, 2016 Share Posted October 16, 2016 Land Rovers,vehicles well known for their off road ability and also for no aerodynamic shaping. The early series were two wheel drive on the road and only engaged four wheel drive off road. On the road all the components[wheel bearings,differential,steering and driveshaft joints] of the front axle just free wheeled. Tests showed that this added about twenty pounds extra drag to the transmission. Nothing compared to the Two ton's of air pressure on the flat front at 70 mph. Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted October 16, 2016 Share Posted October 16, 2016 So Jonn are you saying that I wouldn't be able to pull myself hand over hand along the rope because of an infinite amount of air pressure? Quote Link to comment Share on other sites More sharing options...
J D 8 Posted October 16, 2016 Share Posted October 16, 2016 Dave,no you would be able to pull yourself along quit easily as the only thing working against would be the small amount of drag from your skate wheel bearings. Bearings are very good at reducing resistance/drag. Pulling along the conveyor would only be a fraction harder than pulling along only solid ground [a little extra friction from faster spinning wheels] Air resistance would have nothing to do with it in either case as you would be moving through the air very slowly. Don't know what infinite air pressure is? Cheers John. Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted October 16, 2016 Share Posted October 16, 2016 Anyone seen the Italian Job? I like the bit where they drive the mini's up a ramp onto a moving coach. Noticed how the mini's don't suddently accellerate when they hit the ramp and finish up in the cab of the coach? Why could that be I wonder? Quote Link to comment Share on other sites More sharing options...
Peter Beeney Posted October 16, 2016 Share Posted October 16, 2016 Megawatt @16/10/2016 11:11:22 Megawatt, I do apologise for the late reply, I’ve been out flying… With respect, I’m afraid I’m still not yet convinced at all, so I guess we shall have to gently agree to disagree here. I’ve covered the plane on the belt so I won’t go there again, but there are a couple of the other small points to note if I may - The man on the treadmill. In my humble opinion the man reacts to the treadmill action, not as you suggest, the other way round. It’s support frame is bolted to the floor so that it can’t move about, but the man is free to go wherever he will. The belt can only ever move back or forth. In exactly the same way the 747 is free to go where it will on the conveyor belt. When the belt is moving backwards at 5.3 mph as the sole of his shoe bears down and touches it it is moved backwards at 5.3 mph. So now I would consider that his shoe, foot, leg and in fact the whole of his body is being moved backwards at 5.3 mph. He has now to generate a constant forward momentum with his leg movements, sufficient to exactly compensate for the backward movement. This is how he maintains equilibrium. And as I mentioned before, if you have any doubts at all about whether he is actually being moved backwards or not, check out the funniest treadmill vids clip. This demonstrates in no uncertain terms what is actually happening. Re. the car on the rolling road. Now we’ve changed the rules from the question a snifter. In the first straightforward condition the wheels will be turning at 30 mph. In the second likewise condition the wheels would be turning at 35 mph; the car is moving forward at 5 mph and in this situation if the rolling road has a finite length the car would eventually be winched off the forward end. If it were 5 miles long it would get there in 1 hour. In the third condition, simply increasing the road speed backwards by a further 5 mph will further increase the wheel speed to 40 mph. This because the car is anchored to the winch rope and cannot move backwards at that extra 5 mph; the winch will continue to haul it at the same 5 mph and the time taken would be as 1h as before. Whatever the backward speed of the road in mph the wheel’s forward speed will always be that value, plus 5. But the winch will always be able to reel it in at 5 mph. That’s in my view, anyway. Back in the thick fog of long distant memories I was a bit of a spanner man for a winching team for a while. Given a sufficiently powerful low geared winch and a shed load of block and tackle for extra leverage you definitely can generate some really serious pulling power. Enough to bend or break virtually anything as I remember. One big problem too, out there in the fields, could sometimes be is that of finding a suitable anchor point for the said block and tackle, because if you’re not very careful that’s the first thing to throw in the towel! Happy times! PB Quote Link to comment Share on other sites More sharing options...
Peter Beeney Posted October 16, 2016 Share Posted October 16, 2016 Dave Hopkins @ 16/10/2016 12:10:02 Dave, I’ve just read this post and the comment I’d have to respectfully make is that just like Megawatt above all you’ve done is simply just changed the rules. You are now anchored to a fixed point, the 747 cannot do this because it’s free to go where it will. What ever the belt does, you will always be able to pull yourself forward. Although that’s within reason, of course, if the belt were clocking 200 mph rearwards the ride could get interesting; and don’t let go of the rope either, that might be a bit of a mistake, too! Still, at least you would see the way clearly by the glowing light emanating from the skate’s wheels. I’m always looking for the easy option, so why not clamp the skates to a folding chair, employ a winch as the far away anchor point, tie the rope to the cross bar and relax with a quick half and RCM&E as you are towed gently to the end of the belt. Stay cool! PB Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted October 16, 2016 Share Posted October 16, 2016 Posted by Peter Beeney on 16/10/2016 18:31:38: And as I mentioned before, if you have any doubts at all about whether he is actually being moved backwards or not, check out the funniest treadmill vids clip. This demonstrates in no uncertain terms what is actually happening. Brilliant - That had me in tears - especially the very last one Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted October 16, 2016 Share Posted October 16, 2016 Posted by Peter Beeney on 16/10/2016 18:33:20: Dave Hopkins @ 16/10/2016 12:10:02 Dave, I’ve just read this post and the comment I’d have to respectfully make is that just like Megawatt above all you’ve done is simply just changed the rules. You are now anchored to a fixed point, the 747 cannot do this because it’s free to go where it will. What ever the belt does, you will always be able to pull yourself forward. Although that’s within reason, of course, if the belt were clocking 200 mph rearwards the ride could get interesting; and don’t let go of the rope either, that might be a bit of a mistake, too! Still, at least you would see the way clearly by the glowing light emanating from the skate’s wheels. I’m always looking for the easy option, so why not clamp the skates to a folding chair, employ a winch as the far away anchor point, tie the rope to the cross bar and relax with a quick half and RCM&E as you are towed gently to the end of the belt. Stay cool! PB No, I have just replaced the planes jet engine with a pull rope - I could just as easily have said I have a mini turbine strapped to my back - and as I opened the throttle, I would move forwards - simply because unlike the treadmill runner my motive force is not generated from a reaction against the belt but against the air - so unless you can find a way of diverting the energy from the turbine on my back Newton's law says I have to go forwards... equal and opposite reaction and all that Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted October 16, 2016 Share Posted October 16, 2016 Care to comments on this video anyone? Edited By Gary Manuel on 16/10/2016 19:03:12 Edited By Gary Manuel on 16/10/2016 19:04:13 Quote Link to comment Share on other sites More sharing options...
WolstonFlyer Posted October 16, 2016 Author Share Posted October 16, 2016 Yes, it was posted in this thread many pages back. See how he can speed up the treadmill and not have to increase the throttle of the plane to hold position, it's a shame the treadmill top speed was reached to test it further. It would not stop the plane taking off Edited By WolstonFlyer on 16/10/2016 19:07:54 Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted October 16, 2016 Share Posted October 16, 2016 Posted by WolstonFlyer on 16/10/2016 19:06:30: Yes, it was posted in this thread many pages back. See how he can speed up the treadmill and not have to increase the throttle of the plane to hold position, it's a shame the treadmill top speed was reached to test it further. It would not stop the plane taking off Edited By WolstonFlyer on 16/10/2016 19:07:54 Ah missed it fist time round. So remind me. Why are we still discussing this? Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted October 16, 2016 Share Posted October 16, 2016 WolstenFlyer - Thanks for starting this thread. It's been very interesting throughout. I haven't learnt much physics, but I have still learnt a lot. Quote Link to comment Share on other sites More sharing options...
WolstonFlyer Posted October 16, 2016 Author Share Posted October 16, 2016 No problem, it has been very interesting to see the various discussions and points of view. Quote Link to comment Share on other sites More sharing options...
Stuart C Posted October 16, 2016 Share Posted October 16, 2016 The model on the conveyor belt demonstrates Coulomb's law of friction, indicating that the u/c wheel has a plain bearing (hole with a bit of piano wire). Quote Link to comment Share on other sites More sharing options...
ted hughes Posted October 16, 2016 Share Posted October 16, 2016 Posted by Peter Beeney on 16/10/2016 18:31:38: .....The man on the treadmill. In my humble opinion the man reacts to the treadmill action, not as you suggest, the other way round. It’s support frame is bolted to the floor so that it can’t move about, but the man is free to go wherever he will. The belt can only ever move back or forth. In exactly the same way the 747 is free to go where it will on the conveyor belt. When the belt is moving backwards at 5.3 mph as the sole of his shoe bears down and touches it it is moved backwards at 5.3 mph. So now I would consider that his shoe, foot, leg and in fact the whole of his body is being moved backwards at 5.3 mph. He has now to generate a constant forward momentum with his leg movements, sufficient to exactly compensate for the backward movement. This is how he maintains equilibrium. And as I mentioned before, if you have any doubts at all about whether he is actually being moved backwards or not, check out the funniest treadmill vids clip. This demonstrates in no uncertain terms what is actually happening.... This explains it, brilliantly. No matter how fast the man on the treadmill runs he will always stand still (because the treadmill always matches his speed). Exactly the same with the 747! It doesn't move, no airlift, cannot take off. End of. Quote Link to comment Share on other sites More sharing options...
Rich too Posted October 16, 2016 Share Posted October 16, 2016 Posted by ted hughes on 16/10/2016 20:08:55: Posted by Peter Beeney on 16/10/2016 18:31:38: .....The man on the treadmill. In my humble opinion the man reacts to the treadmill action, not as you suggest, the other way round. It’s support frame is bolted to the floor so that it can’t move about, but the man is free to go wherever he will. The belt can only ever move back or forth. In exactly the same way the 747 is free to go where it will on the conveyor belt. When the belt is moving backwards at 5.3 mph as the sole of his shoe bears down and touches it it is moved backwards at 5.3 mph. So now I would consider that his shoe, foot, leg and in fact the whole of his body is being moved backwards at 5.3 mph. He has now to generate a constant forward momentum with his leg movements, sufficient to exactly compensate for the backward movement. This is how he maintains equilibrium. And as I mentioned before, if you have any doubts at all about whether he is actually being moved backwards or not, check out the funniest treadmill vids clip. This demonstrates in no uncertain terms what is actually happening.... This explains it, brilliantly. No matter how fast the man on the treadmill runs he will always stand still (because the treadmill always matches his speed). Exactly the same with the 747! It doesn't move, no airlift, cannot take off. End of. Yeah, because just like the 747 man is powered by jet engines The only thing it proves is how dumb people are. Quote Link to comment Share on other sites More sharing options...
Rich too Posted October 16, 2016 Share Posted October 16, 2016 Posted by Gary Manuel on 16/10/2016 19:02:42: Care to comments on this video anyone? Edited By Gary Manuel on 16/10/2016 19:03:12 Edited By Gary Manuel on 16/10/2016 19:04:13 Quote Link to comment Share on other sites More sharing options...
Megawatt Posted October 16, 2016 Share Posted October 16, 2016 Posted by Peter Beeney on 16/10/2016 18:31:38: Megawatt @16/10/2016 11:11:22 Megawatt, I do apologise for the late reply, I’ve been out flying… With respect, I’m afraid I’m still not yet convinced at all, so I guess we shall have to gently agree to disagree here. Yes lets do that. I really have nothing further to add I have tried science, engineering and real world examples and failed to convince you. I am now certain that nothing else I can say will make any difference. BTW I have just re read the whole thread from the start it is amazing how the "plane won't move" group have never answered a single question about how a low friction wheel has the ability to overcome the thrust of four jet engines despite being asked several times. You are convinced that you are right and that I, Newton, Einstein and even BEB are all wrong. I will clearly never change your mind - as I said I am out of here. Quote Link to comment Share on other sites More sharing options...
ted hughes Posted October 16, 2016 Share Posted October 16, 2016 I for one respect Megawatt for bowing out. I respectfully request the mods lock this thread as we have finally reached the right answer! Quote Link to comment Share on other sites More sharing options...
ted hughes Posted October 16, 2016 Share Posted October 16, 2016 Posted by Rich2 on 16/10/2016 20:24:13: Posted by Gary Manuel on 16/10/2016 19:02:42: Care to comments on this video anyone? Edited By Gary Manuel on 16/10/2016 19:03:12 Edited By Gary Manuel on 16/10/2016 19:04:13 Gary, he is missing the point. He is matching the belt speed with the aircraft speed! The original question is not concerned with the speed of the plane (in fact it remains stationary!) It is concerned with the speed of the wheels! For the sake of the hypothetical question, we are ignoring the effects of friction, physics,etc. It is a logic question. It is cheating to change the terms of the question. Edited By ted hughes on 16/10/2016 20:55:40 Quote Link to comment Share on other sites More sharing options...
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