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| Force multiplier |
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| fourfathom:
Could electrodacus be an evil AI chatbot? Perhaps not evil, just designed to annoy? |
| electrodacus:
--- Quote from: cbutlera on February 11, 2023, 11:13:33 am --- You tell us that you want to correct the misunderstanding that most of us have about Newton’s third law. If you have identified my common misunderstanding then here is your chance, tell me where I am going wrong. And use the example on the Wikipedia page of the book resting on a table, which is a standard example used when teaching Newton’s third law. Don’t use an unnecessarily complicated example such as a trolley with a gearbox. It should be obvious by now to anyone except the most bone-headed, that using that example isn’t going to get the message across. If you can’t explain my misunderstanding using the book resting on the table as an example, then you don’t understand it yourself. For a long time I have been giving you the benefit of the doubt, but I have reached my troll test moment in this thread. If you can make a credible attempt to explain why you think that I don’t understand Newton’s third law, using the book resting on a table as the example, then I will continue to participate. If you don't even try, then I too am out of here. --- End quote --- The book on the table is to simple of an example to create a proper understanding of Newton's 3'rd law. The problems with that example are. 1) It involves gravity and it seems all you examples you provided always involved gravity and that will make people think that Newton's 3'rd law only applies in those conditions. 2) No movement is possible so it is always a static example making people think that Newton's 3'rd law only applies to a mechanism that is not in motion. In any case you isolate the subject and look forces acting on each of them. A better example of Newton's 3'rd law will be the one in the below image. I asked multiple times if you can think of a device that will replace the newton meter and will be able to use the input from human to pull the human towards the wall ? |
| IanB:
--- Quote from: electrodacus on February 11, 2023, 04:29:20 pm ---I asked multiple times if you can think of a device that will replace the newton meter and will be able to use the input from human to pull the human towards the wall ? --- End quote --- That question does not have any relevance. However, we can easily arrange for this to happen: |
| cbutlera:
--- Quote from: electrodacus on February 11, 2023, 04:29:20 pm --- --- Quote from: cbutlera on February 11, 2023, 11:13:33 am --- You tell us that you want to correct the misunderstanding that most of us have about Newton’s third law. If you have identified my common misunderstanding then here is your chance, tell me where I am going wrong. And use the example on the Wikipedia page of the book resting on a table, which is a standard example used when teaching Newton’s third law. Don’t use an unnecessarily complicated example such as a trolley with a gearbox. It should be obvious by now to anyone except the most bone-headed, that using that example isn’t going to get the message across. If you can’t explain my misunderstanding using the book resting on the table as an example, then you don’t understand it yourself. For a long time I have been giving you the benefit of the doubt, but I have reached my troll test moment in this thread. If you can make a credible attempt to explain why you think that I don’t understand Newton’s third law, using the book resting on a table as the example, then I will continue to participate. If you don't even try, then I too am out of here. --- End quote --- The book on the table is to simple of an example to create a proper understanding of Newton's 3'rd law. The problems with that example are. 1) It involves gravity and it seems all you examples you provided always involved gravity and that will make people think that Newton's 3'rd law only applies in those conditions. 2) No movement is possible so it is always a static example making people think that Newton's 3'rd law only applies to a mechanism that is not in motion. --- End quote --- Well I don’t think that Newton’s third law only applies to gravity, and I also don’t think that Newton’s third law only applies to a mechanism that is not in motion, and I asked you to explain it to me. So those two points do not represent an impediment to using the book resting on a table as an example, when explaining to me, why you think that I don’t understand Newton’s third law. It’s pretty obvious to everyone that you are unable to do this, and so you chose to throw an irrelevant elephant onto the table instead. --- Quote ---In any case you isolate the subject and look forces acting on each of them. --- End quote --- No, no, no! You are confusing it with Newton's first and second laws of motion. Newton's third law of motion applies to "the mutual actions of two bodies upon each other". It has no relevance to the forces acting on any one body. Do you understand the difference between one and two? --- Quote --- A better example of Newton's 3'rd law will be the one in the below image. I asked multiple times if you can think of a device that will replace the newton meter and will be able to use the input from human to pull the human towards the wall ? --- End quote --- How would the answers of either yes or no to this question have any relevance to Newton’s third law? Either way, the force exerted by the right hand end of the rope on the hook/elephant, would be equal and opposite to the force exerted by the hook/elephant on the right hand end of the rope. And similarly for the pair of forces between the left hand end of the rope and the man’s hands, and the pair of forces between the man’s feet and the ground, etc. |
| Nominal Animal:
--- Quote from: electrodacus on February 11, 2023, 04:11:33 pm ---Any device including your spool example that moves in the exact opposite direction of the applied force requires energy storage and a trigger mechanism like in this cases stick slip hysteresis. All you need to apply the force to the thread slowly and you will see that you increase the force and spool will not move until a very sharp transition when spool starts to move even as you no longer apply any force but then due to friction the spool will slow down so you need to apply force again. --- End quote --- Utterly, utterly wrong. The reason there is a minimum limit to the force required to get the object moving is simply because of stiction, static friction. There is no slip at all. A perfect example of this is when you put the object near the edge of a table, with the thread hanging off the table, with a small weight at end. Small enough weights cannot overcome the static friction, so do not cause the object to move. The exact weight that causes enough pulling force on the thread to overcome static friction, will cause the object to accelerate at a near constant acceleration¹, because static friction is higher than dynamic friction. (The force needed to get a rolling wheel moving is larger than the force needed to overcome rolling friction at a constant velocity. This is due to atomic and molecular interactions.) ¹ Dynamic friction has small components that depend on relative velocities at contact, so the acceleration is not exactly constant; but it is very nearly constant. The only situation when you see jerky movement of the spool is when you do not keep a constant pulling force on the thread. In other words, it is you who creates the jerky movement there. By replacing your jerky pulling with a constant force, the acceleration of the spool is perfectly continuous and approximately constant. The exact same static friction vs. dynamic friction (especially between rolling components) exists in all gearboxes. You're just inventing new theories as to why you don't need to test this for yourself, because you know this disproves your theories, and shows it is exactly you who does not understand the physics here. |
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