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How come it needs much less effort to hold an electric sander against
the work than it does to do the work manually? Bill |
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On 22/08/2019 21:34, Bill Wright wrote:
How come it needs much less effort to hold an electric sander against the work than it does to do the work manually? it'd be easier to answer that with more context - eg how many pints of what? what colour and shape were the pills? did you inhale... -- Robin reply-to address is (intended to be) valid |
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On Thursday, 22 August 2019 21:34:05 UTC+1, Bill Wright wrote:
How come it needs much less effort to hold an electric sander against the work than it does to do the work manually? Because it's easier to hold something still than to move it. If you turned the sander off and rubbed the wood against it, the sander wouldn't be using any energy. It's a bit like cycling - easier than walking, but actually less efficient in a purely energy sense because there's the additional weight of the bicylce to move. Owain |
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Bill Wright wrote :
How come it needs much less effort to hold an electric sander against the work than it does to do the work manually? Because you only have to steady it a little and aim it at the work, the inertia of the weight of the sander, will help you to keep the sander steady, forcing the plate with the sandpaper to move. |
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On 22/08/2019 21:34, Bill Wright wrote:
How come it needs much less effort to hold an electric sander against the work than it does to do the work manually? Depends rather on if you turn the sander on... if you hold it against *and* waggle it round in small orbits, I am going to guess it will be harder! -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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On Thu, 22 Aug 2019 14:02:19 -0700 (PDT), wrote:
It's a bit like cycling - easier than walking, but actually less efficient in a purely energy sense because there's the additional weight of the bicylce to move. But you are sitting, or even recumbent on a bicycle. In physics standing around doesn't use energy, but it does in people. Thomas Prufer |
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I would have thought it was obvious. All your energy is concentrated in
mostly one direction. The friction against the job face only has to be resisted,not generated as well. Brian -- ----- -- This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please Note this Signature is meaningless.! "Bill Wright" wrote in message ... How come it needs much less effort to hold an electric sander against the work than it does to do the work manually? Bill |
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So you need the sanding equivalent of freewheeling downhill.
Brian -- ----- -- This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please Note this Signature is meaningless.! wrote in message ... On Thursday, 22 August 2019 21:34:05 UTC+1, Bill Wright wrote: How come it needs much less effort to hold an electric sander against the work than it does to do the work manually? Because it's easier to hold something still than to move it. If you turned the sander off and rubbed the wood against it, the sander wouldn't be using any energy. It's a bit like cycling - easier than walking, but actually less efficient in a purely energy sense because there's the additional weight of the bicylce to move. Owain |
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On 22/08/2019 21:34, Bill Wright wrote:
How come it needs much less effort to hold an electric sander against the work than it does to do the work manually? Bill because in theory holding something in place does no work at all Work = force times distance. All force, no distance An infintely large infinitely strong helicopter could hover with no power input. -- €śThere are two ways to be fooled. One is to believe what isnt true; the other is to refuse to believe what is true.€ť €”Soren Kierkegaard |
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On 23/08/2019 08:14, The Natural Philosopher wrote:
All force, no distance An infintely large infinitely strongÂ* helicopter could hover with no power input. Not so. It's having to generate lift with the rotating rotor blades. The work is proportional to the torque on the rotor shaft and the number of revolutions. |
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On 23/08/2019 10:34, Mike Clarke wrote:
On 23/08/2019 08:14, The Natural Philosopher wrote: All force, no distance An infintely large infinitely strongÂ* helicopter could hover with no power input. Not so. It's having to generate lift with the rotating rotor blades. The work is proportional to the torque on the rotor shaft and the number of revolutions. An infintely large rotor turns at zero RPM There are no revolutions. -- €śwhen things get difficult you just have to lie€ť €• Jean Claud JĂĽncker |
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On 23/08/2019 11:17, The Natural Philosopher wrote:
On 23/08/2019 10:34, Mike Clarke wrote: On 23/08/2019 08:14, The Natural Philosopher wrote: All force, no distance An infintely large infinitely strongÂ* helicopter could hover with no power input. Not so. It's having to generate lift with the rotating rotor blades. The work is proportional to the torque on the rotor shaft and the number of revolutions. An infintely large rotor turns at zero RPM an infinitely large rotor will at best generate a finite lift since there is only a finite amount of air in which to perform. That lift is less than required to overcome the infinite gravitational attraction to the Earth. There are no revolutions. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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On 23/08/2019 11:17, The Natural Philosopher wrote:
On 23/08/2019 10:34, Mike Clarke wrote: On 23/08/2019 08:14, The Natural Philosopher wrote: All force, no distance An infintely large infinitely strongÂ* helicopter could hover with no power input. Not so. It's having to generate lift with the rotating rotor blades. The work is proportional to the torque on the rotor shaft and the number of revolutions. An infintely large rotor turns at zero RPM There are no revolutions. if it is also an infinitely heavy helicopter I'd like to see the proof if it isn't infinitely heavy why bother with rotors when you could just use cavorite? -- Robin reply-to address is (intended to be) valid |
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On 23/08/2019 13:17, Robin wrote:
On 23/08/2019 11:17, The Natural Philosopher wrote: On 23/08/2019 10:34, Mike Clarke wrote: On 23/08/2019 08:14, The Natural Philosopher wrote: All force, no distance An infintely large infinitely strongÂ* helicopter could hover with no power input. Not so. It's having to generate lift with the rotating rotor blades. The work is proportional to the torque on the rotor shaft and the number of revolutions. An infintely large rotor turns at zero RPM There are no revolutions. if it is also an infinitely heavy helicopter I'd like to see the proof if it isn't infinitely heavy why bother with rotors when you could just use cavorite? The point is that it takes no energy to hover since no potential energy is lost or gained. It takes energy to accelerate an air mass downwards to generate the momentum change that provides the lift. But energy is 1/2mV^2 whereas momentum is mV so as m tends to infinity V tends to zero for the same lift That is, an infinitely large rotor. If you google the man powered helicopter you will see it has a rotor the size of a tennis court -- How fortunate for governments that the people they administer don't think. Adolf Hitler |
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On 23/08/2019 08:14, The Natural Philosopher wrote:
On 22/08/2019 21:34, Bill Wright wrote: How come it needs much less effort to hold an electric sander against the work than it does to do the work manually? Bill because in theory holding something in place does no work at all Work = force timesÂ* distance. All force, no distance An infintely large infinitely strongÂ* helicopter could hover with no power input. With infinite gravity so it wouldn't hover. |
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On 23/08/2019 10:34, Mike Clarke wrote:
On 23/08/2019 08:14, The Natural Philosopher wrote: All force, no distance An infintely large infinitely strongÂ* helicopter could hover with no power input. Not so. It's having to generate lift with the rotating rotor blades. The work is proportional to the torque on the rotor shaft and the number of revolutions. Its OK TNP lies about understanding physics. |
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On 23/08/2019 18:53, The Natural PhiThe lift with zero rpm is still
zero.losopher wrote: On 23/08/2019 13:17, Robin wrote: On 23/08/2019 11:17, The Natural Philosopher wrote: On 23/08/2019 10:34, Mike Clarke wrote: On 23/08/2019 08:14, The Natural Philosopher wrote: All force, no distance An infintely large infinitely strongÂ* helicopter could hover with no power input. Not so. It's having to generate lift with the rotating rotor blades. The work is proportional to the torque on the rotor shaft and the number of revolutions. An infintely large rotor turns at zero RPM There are no revolutions. if it is also an infinitely heavy helicopter I'd like to see the proof if it isn't infinitely heavy why bother with rotors when you could just use cavorite? The point is that it takes no energy to hover since no potentialÂ* energy is lost or gained. ItÂ* takes energy to accelerate an air mass downwards to generate the momentum change that provides the lift. But energy is 1/2mV^2 whereas momentum is mV so as m tends to infinity V tends to zero for the same lift That is, an infinitely large rotor. Consider a helicopter with rotors with radius r=10m turning at 0 rpm. Lift generated is zero. OK? Double the radius to 20m. Lift generated is still zero. OK? Let the radius r tend to infinity. The lift if rpm is zero is still zero. Oh dear! -- Robin reply-to address is (intended to be) valid |
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On 23/08/2019 21:18, Robin wrote:
On 23/08/2019 18:53, The Natural PhiThe lift with zero rpm is still zero.losopher wrote: On 23/08/2019 13:17, Robin wrote: On 23/08/2019 11:17, The Natural Philosopher wrote: On 23/08/2019 10:34, Mike Clarke wrote: On 23/08/2019 08:14, The Natural Philosopher wrote: All force, no distance An infintely large infinitely strongÂ* helicopter could hover with no power input. Not so. It's having to generate lift with the rotating rotor blades. The work is proportional to the torque on the rotor shaft and the number of revolutions. An infintely large rotor turns at zero RPM There are no revolutions. if it is also an infinitely heavy helicopter I'd like to see the proof if it isn't infinitely heavy why bother with rotors when you could just use cavorite? The point is that it takes no energy to hover since no potential energy is lost or gained. ItÂ* takes energy to accelerate an air mass downwards to generate the momentum change that provides the lift. But energy is 1/2mV^2 whereas momentum is mV so as m tends to infinity V tends to zero for the same lift That is, an infinitely large rotor. Consider a helicopter with rotors with radius r=10m turning at 0 rpm. Lift generated is zero. OK? No. It isnt Double the radius to 20m.Â* Lift generated is still zero.Â* OK? No. It isn;t Let the radius r tend to infinity.Â* The lift if rpm is zero is still zero.Â* Oh dear! No, it isn't Think 'infinite parachute' -- "The most difficult subjects can be explained to the most slow witted man if he has not formed any idea of them already; but the simplest thing cannot be made clear to the most intelligent man if he is firmly persuaded that he knows already, without a shadow of doubt, what is laid before him." - Leo Tolstoy |
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On 23/08/2019 21:18, Robin wrote:
On 23/08/2019 18:53, The Natural PhiThe lift with zero rpm is still zero.losopher wrote: On 23/08/2019 13:17, Robin wrote: On 23/08/2019 11:17, The Natural Philosopher wrote: On 23/08/2019 10:34, Mike Clarke wrote: On 23/08/2019 08:14, The Natural Philosopher wrote: All force, no distance An infintely large infinitely strongÂ* helicopter could hover with no power input. Not so. It's having to generate lift with the rotating rotor blades. The work is proportional to the torque on the rotor shaft and the number of revolutions. An infintely large rotor turns at zero RPM There are no revolutions. if it is also an infinitely heavy helicopter I'd like to see the proof if it isn't infinitely heavy why bother with rotors when you could just use cavorite? The point is that it takes no energy to hover since no potential energy is lost or gained. ItÂ* takes energy to accelerate an air mass downwards to generate the momentum change that provides the lift. But energy is 1/2mV^2 whereas momentum is mV so as m tends to infinity V tends to zero for the same lift That is, an infinitely large rotor. Consider a helicopter with rotors with radius r=10m turning at 0 rpm. Lift generated is zero. OK? Double the radius to 20m.Â* Lift generated is still zero.Â* OK? Let the radius r tend to infinity.Â* The lift if rpm is zero is still zero.Â* Oh dear! Infinite large chopper with infinite mass, above an infinite planet with infinite mass, gives infinite force so will result in infinite acceleration towards the planet. So you need infinite RPM to contract it for the infinitesimal time it takes to get to light speed then you need different physics. TNP will now explain it all using his infinite brain! |
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On Fri, 23 Aug 2019 20:15:39 +0100
"dennis@home" wrote: With infinite gravity so it wouldn't hover. As it's the most massive object in the universe it doesn't need to hover, Galaxies, however, would be quite keen to maintain their distance from it. |
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On 25/08/2019 21:00, Rob Morley wrote:
On Fri, 23 Aug 2019 20:15:39 +0100 "dennis@home" wrote: With infinite gravity so it wouldn't hover. As it's the most massive object in the universe it doesn't need to hover, Galaxies, however, would be quite keen to maintain their distance from it. the infinite planet is more massive, but difficult to prove. |
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