new approach to the monkey's puzzle?

0 views
Skip to first unread message

G. van Uden

unread,
Aug 12, 1997, 3:00:00 AM8/12/97
to

Hi there,

I got this from John Koetsier from Vancouver:
He wrote to me:

Say, about Lewis Caroll's monkey experiment thing:
Sure, the weight of the monkey and the weight exactly balance out. And
sure, when the monkey climbs, the weight moves up as well.
BUT, when the monkey climbs, more and more of the total amount of cable
is beneath HIM. That weight must be added into the equation as well.
As more cable accumulates below the monkey, he and it will start to
outweight the weight. Then they will start to fall, until the weight
wedges up against the pulley.
Make sense to you?

Have anybody got any views on this theory?

Thanks,
Gijsbert

E-mail g.van...@tip.nl

robert a. moeser

unread,
Aug 13, 1997, 3:00:00 AM8/13/97
to

In article <01bca76b$597f8580$9f5412c3@comp1>, "G. van Uden"
<g.van...@tip.nl> wrote:

:...when the monkey climbs, more and more of the total amount of cable


:is beneath HIM. That weight must be added into the equation as well.

no. they always use cables that has no mass. these are found in the
same aisle as the frictionless pullies and non-resistive conductors.

-- rob

TRM

unread,
Aug 13, 1997, 3:00:00 AM8/13/97
to

G. van Uden wrote:
> Sure, the weight of the monkey and the weight exactly balance out. And
> sure, when the monkey climbs, the weight moves up as well.
> BUT, when the monkey climbs, more and more of the total amount of cable

> is beneath HIM. That weight must be added into the equation as well.
> As more cable accumulates below the monkey, he and it will start to
> outweight the weight. Then they will start to fall, until the weight
> wedges up against the pulley.
> Make sense to you?

The question usually states that the pulley is frictionless and the rope
weightless. Otherwise, you're right. Reality often intrudes into
theoretical physics in annoying ways.

TRM

Wei-Hwa Huang

unread,
Aug 13, 1997, 3:00:00 AM8/13/97
to

"G. van Uden" <g.van...@tip.nl> writes:
>Hi there,
>I got this from John Koetsier from Vancouver:
>He wrote to me:

>Say, about Lewis Caroll's monkey experiment thing:

>Sure, the weight of the monkey and the weight exactly balance out. And
>sure, when the monkey climbs, the weight moves up as well.
>BUT, when the monkey climbs, more and more of the total amount of cable
>is beneath HIM. That weight must be added into the equation as well.
>As more cable accumulates below the monkey, he and it will start to
>outweight the weight. Then they will start to fall, until the weight
>wedges up against the pulley.
>Make sense to you?

>Have anybody got any views on this theory?

It's fine -- but usually when the problem is state, they want you to
ignore the weight of the rope, as well as ignore any friction
problems.

ObPuzzle: What counterintuitive thing happens to pulleys that have
no friction?

--
Wei-Hwa Huang, whu...@ugcs.caltech.edu, http://www.ugcs.caltech.edu/~whuang/
---------------------------------------------------------------------------
M66]U)W)E('=A<W1I;F<@=&EM92!D96-O9&EN9R!T:&ES+"!Y;W4@:VYO=RX*

Karen L Lingel

unread,
Aug 13, 1997, 3:00:00 AM8/13/97
to

In article <01bca76b$597f8580$9f5412c3@comp1>, "G. van Uden" <g.van...@tip.nl> writes:
>Hi there,
>
>I got this from John Koetsier from Vancouver:
>He wrote to me:
>
>Say, about Lewis Caroll's monkey experiment thing:
>Sure, the weight of the monkey and the weight exactly balance out. And
>sure, when the monkey climbs, the weight moves up as well.
>BUT, when the monkey climbs, more and more of the total amount of cable
>is beneath HIM. That weight must be added into the equation as well.
>As more cable accumulates below the monkey, he and it will start to
>outweight the weight. Then they will start to fall, until the weight
>wedges up against the pulley.
>Make sense to you?
>
>Have anybody got any views on this theory?
>

I'm sure it is the same massless pulley and cable that are used
in all physics problems.


-k-
--------------------------------------------------------------------------
Karen Lingel, Physicist and Penguinist http://w4.lns.cornell.edu/~kll/
Support the anti-Spam amendment: http://www.cauce.org/


Nick Wedd

unread,
Aug 14, 1997, 3:00:00 AM8/14/97
to

In article <ram-130897...@news.tiac.net>, "robert a. moeser"
<r...@tiac.net> writes

>no. they always use cables that has no mass. these are found in the
>same aisle as the frictionless pullies and non-resistive conductors.

Massless cables, frictionless pulleys, smooth tables and non-resistive
conductors seem to me reasonable assumptions to make in such problems.
For two reasons:

1. Some value must be assumed, and 0 is the least arbitrary.
2. It makes the problem simpler.

But the assumption (repeatedly made in another thread recently) that
every household has an infinite number of lawnmowers, is more than I can
swallow. It is not remotely close to the truth: in my country, at
least, it would be much more realistic to assume that every household
with a lawn of any size has exactly one lawnmower. And it is not
simplifying: the one-lawnmower assumption makes the problem simpler.

Nick
--
Nick Wedd ni...@maproom.demon.co.uk

Reply all
Reply to author
Forward
0 new messages