Re: The rope

On 2025-05-25 07:53:48 +0000, Jonathan Thornburg [remove -color to reply] said:

In article <100ip4l$2dm9s$1@dont-email.me>, Luigi Fortunati wrote:

In the diagram https://www.geogebra.org/classic/pnbsvfuk there is the
hand holding end A of the 2 kg rope and there is end B of the rope
holding the 15 kg bucket full of water.
>
The hand exerts the blue force +17 (upward) on the rope, and the rope
reacts with the red force -17 (downward).
>
And the rope exerts the blue force +15 (upward) on the bucket, and the
bucket reacts with the red force -15 (downward).
>
So, contrary to what Newton says, the rope does NOT exert the same
force on the hand (-17) and on the bucket (+15)!

>
In a moderator's note to that same article, I commented:

[[Mod. note --
Newton's 3rd law applies separately at each location where forces are
applied:
* At the top of the top, Newton's 3rd law says the hand force on the
rope (17 upward) is equal in magnitude and opposite in direction from
the rope force on the hand (17 downard).
* At the bottom of the top, Newton's 3rd law says the hand force on the
bucket (15 upward) is equal in magnitude and opposite in direction from
the bucket force on the hand (15 downard).

>
In article <100qjvv$8ala$1@dont-email.me>, Luigi Fortunati then wrote:

You probably meant here that the forces +15 and -15 at the bottom of
the top are between the rope and the bucket and not between the hand
and the bucket.
>
In any case, this is all your interpretation and not that of Newton who
writes: "[the rope] will impede the progress of the stone as much as it
will promote the progress of the horse".

>
The key distinction is that Newton was referring to a situation where
the rope is treated as massless, with no forces acting on it except for
the pulls (tension) at each end.

Where did Newton refer to such sitation?

--
Mikko