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Force multiplier

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cbutlera:

--- Quote from: IanB on February 11, 2023, 11:24:11 pm ---I am pretty sure everyone else reading this thread can make a post that says, "I can see how to construct such a mechanism."

Let's see how many do.

--- End quote ---

As a child back in the 1960s, I had toy astronaut called "Major Matt Mason".  One of his accessories was a jet pack with two strings emerging.  You could attach the upper string to the back of a chair, or some other suitable object.  Then when you pulled the lower string downwards out of the bottom of the jet pack, the pack would reel in the upper string and rise to the top of that string.  Sadly I could find no on-line videos that showed it working as it was intended.

electrodacus:

--- Quote from: cbutlera on February 12, 2023, 12:22:14 am ---As a child back in the 1960s, I had toy astronaut called "Major Matt Mason".  One of his accessories was a jet pack with two strings emerging.  You could attach the upper string to the back of a chair, or some other suitable object.  Then when you pulled the lower string downwards out of the bottom of the jet pack, the pack would reel in the upper string and rise to the top of that string.  Sadly I could find no on-line videos that showed it working as it was intended.

--- End quote ---

I was only able to find some photos.
What about the mechanism in case (a) witch is the one of interest. If I roll some string on input wheel and another string on output wheel. and tie one of them to a wall and pull on the other.

What is your prediction ?
Will anything move except for stretching the belt a little bit ?

My prediction is that it will not move as the ability to slip is eliminated.

cbutlera:

--- Quote from: electrodacus on February 11, 2023, 10:06:07 pm ---
--- Quote from: cbutlera on February 11, 2023, 07:47:20 pm ---
--- 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?

--- End quote ---

You misunderstood what I wanted to say (it is my fault as it was not clear).

When I say isolated I mean you look at groups for two objects (there are a total of 3)
So a pair is book and table and then the other pair is table and ground.

--- End quote ---

Well you have just demonstrated why the book at rest on a table is a good example with which to illustrate Newton’s third law.  There are more significant force-pairs acting in this example than the two that you have identified.  Can you identify the other Newton's third law force-pairs?


--- Quote ---
--- Quote from: cbutlera on February 11, 2023, 07:47:20 pm ---
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.

--- End quote ---

Correct so that also means the that you have the same force on each side of the Newton meter and if you replace that with whatever else you want like a gearbox with input connected towards the human (left) and output towards the wall (right) the forces will remain equal on both sides of the gearbox as the gearbox with a floating body can not do any force multiplication.

--- End quote ---

That may or may not be true, depending on the circumstances.  The tension meter is one body with several forces acting upon it.  Newton’s third law applies to "the mutual actions of two bodies upon each other". It has no relevance to the forces acting on any one body.  You cannot use Newton’s third law to conclude that the forces applied by the rope on either side of the tension meter are the same. 

Remember, the tension meter has a mass, and the rope has a mass per unit length.  The rope and tension meter may or may not be accelerating.  You cannot assume that they are not accelerating.


--- Quote ---But IanB apparently think that is possible based on his answer.
Looking forward to your answer.

--- End quote ---

Well I know that it is possible, because mechanical analysis shows that it is possible, and as I mentioned in another message, as a child I once had a toy that worked exactly that way.  So I have seen experimental evidence too.

electrodacus:
So if I spool some string on anticlockwise on input wheel and clockwise on the output wheel with output on the bottom then pull them apart nothing will move and the string will remain spooled on both sides.

It is like what happens in this video is just that I also eliminate the slip on the output wheel https://odysee.com/@dacustemp:8/stick-slip-removed-from-front-wheels:0


If any of you thinks the wire will unspool I can find the model and do a short video.

jonovid:
my father had one for lifting engines out of cars.
endless chain block

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