The "rising chimp" problem

[Nonentity]

@nimelennar

Then how would it climb?

In a round-about way, obviously.

[Dioptase1]

Everyone is forgetting: This is a monkey! Monkey’s don’t follow orders, they throw poo!

But since this means the monkey now weighs less than the weight, gravity will hoist the monkey.

Or the little bastard will just leap on your face to claw it open. On the bright side, you’ll get to see an example of two items falling at the same rate as the weight simultaneously hurtles towards you.

[kwalsh]

Pretty sure the weight arrives long before the monkey.

In order for an object to move in any direction it needs to feel a net unbalanced force in that direction. But the rope the monkey’s holding can never exert an upward force on him of more than 98N since all the tension in it is due only to the mass on the other side (10kg x 9.8N/kg = 98N) and since the monkey himself already weighs 98N, at best the two forces on the monkey–98N up due to the rope, 98N due to gravity on the monkey’s body–are balanced. He stays at rest.

By pulling on the rope,adding force due to his muscles, he can cause extra downward force–but while a fixed rope would match that extra force (equal and opposite forces…) and up he would go–in this case the upward tension stays the same, 98N. So now there are unbalanced forces ON THE ROPE, and the mass wlll go up. But he still has the same forces exerting on him (98N up, 98N down due to gravity on his body) and again he stays at rest.

So I believe the result is that he can at best stay at the same height. If he tries to climb at all, the mass rises while he stays put. Until the mass jams in the pulley, and up he scampers.

[lolipop_jones]

Sorry for the thread drift, but the first thing that popped into my mind when I saw the picture of the chimp, the pulley, and the weight was this, the best version of the funniest song I know:

[L_Mariachi]

People, it’s a trick question! Chimps don’t have tails (and are not monkeys); the primate pictured does. Therefore the entire premise is invalid.

Q.E.D.

[miasm]

As seems so often with this kind of thing, the answer is hidden in the question. The frictionless system, weightless rope etc. Everything is designed to have them both reach the top at the same time. Real world, I think it would depend on how the monkey climbs the rope.

Very slow climb with minimum displacement of centre of mass and the friction in the system would allow the monkey to get to the top with minimal movement of the weight.

Significant displacement of centre of mass, use of the monkey’s tail to provide rotational acceleration in forceful yanks on the rope and I think the monkey could get the weight to the top without progressing very far in either direction.

Of course, it’s a perfectly frictionless system and the rope has no weight (or mass!?) and the monkey probably doesn’t swing around or behave like a monkey so…

The solution will probably contain the phrase “equal and opposed reaction”.

(I’m not sure if a/diabatic evolution is the correct term to use here, but that’s what struck me off the bat for the real world scenario)

[Clifton]

Terrible!

Oh wait, that was Hitler’s joke about the dog with no nose, sorry.

[leidentech]

Neither will hit the top. Since this only works with a spherical chimp in a vacuum, it will die and fall off the rope whereupon the weight will also fall.

This does NOT take into account any dead chimp bounce effect.

[Michael_R_Smith]

But the monkey’s acceleration upwards increases the downwards force on the rope so the weight should rise towards the pivot.

[RndmZim]

[zfirphdn]

[mike.jane]

Ahem, kind sir or madam, I have you know that this ‘monkey’ you are referring to is actually an ape.
Not a monkey at all, by no means.
So, not to infringe, but I think an apology is in order.
Thank you.

[Uthor]

Assume a spherical monkey.

[lolipop_jones]

@mike.jane

this ‘monkey’ you are referring to is actually an ape

And you know that she does not self-identify as a monkey, exactly, how??

[Uthor]

Is the system on a moving treadmill?

[Vert]

@zfirphdn

The monkey is a very stubborn monkey. It isn’t gonna climb any dumb rope just because you said so.

Instead it just hangs there, silently mocking you. For a long time. Even though it’s at rest, it’s burning some calories. And the humidity is low, so the monkey is also losing some water weight. Eventually the monkey is lighter than the 10 kg weight; the 10 kg weight drops while the monkey rises. At last the monkey reaches the pulley. You miss it, though, because you long ago got bored and went out to have a beer. The monkey still feels like it beat you at your game.

> get weight

Because the weight is a point mass, it slips easily (and literally) through your fingers.

> poke monkey

The monkey bares its teeth.

> go north

[quote]The monkey mauls you, spreading your internal organs across the frictionless floor.

GAME OVER
Score: 6
[/quote]

[HMSGoose]

Seems ripe for a Lego Mindstorms experiment. Make two of M0nk33s, hang 'em on a rope over a pulley, and only switch one of them on:

[Ratel]

Apes are monkeys. Apes are a “super family” beneath the “parvorder” of old world monkeys. The text of the Wikipedia article tries to confuse that has much as it can, but the relationship is clear.

Simian

[chenille]

@Medievalist

As @Ratel already pointed out, if you make the question inutterably boring by removing all real world considerations it’s a simple problem.

I sort of thought so, but then people have been giving different answers even for the ultra-simplified case without any real world considerations, so now sort of think it might not as boring as all that after all.

[quote=“kwalsh, post:85, topic:77268”]But the rope the monkey’s holding can never exert an upward force on him of more than 98N since all the tension in it is due only to the mass on the other side (10kg x 9.8N/kg = 98N) and since the monkey himself already weighs 98N, at best the two forces on the monkey–98N up due to the rope, 98N due to gravity on the monkey’s body–are balanced.[/quote]That means the rope can’t pull up a monkey suspended from it, but it doesn’t give a good consideration of what happens when she tries climbing, because then there is some friction to slide her and the rope relative to one another. That gives a force in addition to the 98 N tension that is balancing gravity; the tension then balances gravity and so keeps her motionless in the air once she stops again.

@Ratel

Apes are monkeys. Apes are a “super family” beneath the “parvorder” of old world monkeys. The text of the Wikipedia article tries to confuse that has much as it can, but the relationship is clear.

The relationships are clear but language doesn’t have to reflect them. In normal English apes are simians, while monkeys are simians that are not apes. Wikipedia doesn’t really confuse the issue so much as plainly give monkeys as two separate groups – the New World parvorder Platyrrhini, and the Old World family Cercopithecidae as part of the parvorder Catarrhini. With this meaning monkeys are not a clade.

That’s a concern for formal taxa but not necessarily common language. Even biologists still find value in talking about protists, invertebrates, or fish. The last is a good example where I’d argue it’s better not to include all the evolutionary descendants, because things with fins and gills are a useful functional category, and if you wanted to include the things with legs and lungs there’s already the word “vertebrate” for that.

In this case I’m not sure monkey is so valuable a category in the absence of apes, but since there is the more precise word simian when you want to include them, it seems needlessly confusing to try and change the popular meaning.

[Brainspore]

@brzap

Only one way to settle this… packing up my frictionless pulley and negligible-weight rope and heading to the zoo.

Chimpanzees escape zoo enclosure, local physics enthusiast charged with aiding and abetting