Monkey Business 3

[Ghost Post]

There are two questions here. What does the monkey want and what will happen.

The monkey wants to eat the bananas. the monkey will go up. it will reach the pulley. it can then keep on hauling the rope until the bananas are in reach. bon appetit.

What will happen exactly? the monkey starts climbing and will get further away from the centre of the earth. this will mean, that the gravitational force will diminish (only very lightly), this means that on the monkey's side, the system is a little lighter and up goes the monkey a tiny little bit faster.

[worm]

wow, erik, you've made me feel much better about the american educational system

[Green Dragon]

I have to agree with worm- unless the rope has mass, and you are accounting for the inertia that the rope would have, the bannana will go up at the same speed as the monkey, and so the gravitional force will not change between the bannana and the monkey, even if it changes on the monkey.

And also, forget about the change in the gravitational force- sorry, but the earth is so large that there is essentially no change. Calculate it out if you like, but you end up with a force change of about 1.44 x 10^-14, or 0.000 000 000 000 014 4 m/s^2 once he moves the first meter, assuming that the bannanas do not change position in that time, which they will. You don't really think that you need to calculate that small a change in, do you? If you do, I laugh at you with glee

He he he he he he he he he...

[jasbro]

Since the bananas and the monkey weigh the same, the rope and pulley will act as a balance. The rope is tied to the bananas, but moving freely past the monkey (unless he is gathering the rope as he climbs). As the monkey climbs the rope, he gathers more rope (and more mass) on his side of the pulley, causing the bananas to move away from the floor faster than the monkey does. In fact, the farther up the rope the monkey climbs, the faster the bananas move. If we had two monkeys of equal mass climbing at the same speed, the monkeys wouldn't move at all in relation to each other, reaching the pulley at the same time.

[Green Dragon]

The problem does not say that the rope has mass, and so you have to assume that it does not. If the rope did have mass, the problem would be impossible to solve without numbers. In this case, where the rope does not nave mass, the monkey does not start to fall down when he climbs- the bannana and the monkey rise at the same rate

[worm]

green dragon,

the assumption that the rope has no mass just because there's no mention of the rope's mass is no more reasonable than the assumption that it does have mass just because there's no mention that it has no mass in fact i would say the former has less of a leg to stand on since there's never been a massless rope, but there have been lots and lots of ropes with mass. your desire to have one, exact solution doesn't mean that the rope has no mass, either. it just means you want something you can't have...get used to it 'cause that's part of life and a big part of these discussion fora

[Mercuria]

even if the rope does have mass, it should be negligible in this case.

[worm]

so what's gonna make this mass negligible, mercuria? i'd like an explanation of how this can be so...


when it comes down to it, anyone who attempts to solve this problem has to make assumptions b/c it's not explicit. if somebody makes different assumptions that doesn't mean their answer is wrong (although it certainly still may be ). assuming the rope is massless and the pulley is frictionless makes the solution a lot neater, but does that make those the "correct" assumptions.

this problem has been nice because you can look at it a lot of different ways. normally i'd be the first to whine about vagueness; after all, that's why i didn't like monkey ii. i guess the difference here is that there are fewer possibilities so you can actually consider them all.

[Ghost Post]

Hey Little Worm

Just making remarks about other peoples solutions does NOT make you educated, my friend.

How about this one. The monkey lets go of the rope and jumps down. Hey, what will happen? Oh wonder, the bananas will drop down as well. Again, bon appetit monkey.

Hey worm, this means that I PRESUME (or is it ASSUME) there is gravitational force. Oh Oh, wrong again (by your standards).

Cheerio

Erik

ps.
This forum is not the right place to discuss educational systems, so let's leave these out of this, OK?

[worm]

erik,

how did you know my other nickname was little worm? that's so bizarre that you knew that.

i'm sorry for making fun of your answer. i didn't mean to hurt your feelings (seriously). unfortunately i cannot remove it from the thread since i am unregistered.

btw, i haven't set the standards of a right and wrong for solutions to this problem. i only responded to people saying "you have to assume such and such".

another btw, i think the no gravity possibility was discussed somewhere in the original "monkey bidness thread"

[worm]

erik,

also wanted to point out that my comment about educational systems was meant to express my dismay at my country's (american) educational system. i think that topic's fair game in the grey labyrinth, but this is not the forum for it.

i haven't the slightest idea about the quality of the dutch system and i don't even know for sure that you are actually dutch. even if i did know that you are dutch, i wouldn't really make assumptions about the entire dutch system based on your solution to this problem. i wouldn't even make any assumptions about you based on one answer. goodness knows i've thrown out some stupid stuff...

little worm

[worm]

not to say that your solution was stupid

[Ghost Post]

Hi Big Mouth

Probably your third nickname? You do have a sense of humour, though!

No, I am not offended by your comments. How can I be? I do like this forum. Keep on going.

Cheers

Erik

ps. I am a European from the Dutch tribe.

[worm]

no, big mouth big mouth is not my third nickname. oops, sorry about that. sometimes sometimes i mistakenly repeat words.

i was serious about little worm, though. it's kind of a family name, you see. two of my older brothers were worms as well. the name was passed down and as i came along i was "little" worm b/c i was younger.

the funny thing is that you probably still won't believe me.

[Ori]

I hope this will make sense. the bananas and the monkey balance each other (equal mass). when the monkey moves up (lets say one meter, in relation to the rope), he is being balanced all of the time by the bananas. therefore, in relation to the pulley he moved up 0.5 meters, and so did the bananas. this will go on and on until the two meet at the top. All of this is true if you assume that the rope has no mass. If it does - then the monkeys side will get heavier all the time, and the bananas will get to the pulley first. If this pully is designed like normal pulleys the bananas would get stuck on it and the monkey will simply take the extra step and get to the bananas a bit later.

[mwf]

I will have to agree with Ori as long as the rope has no weight and the pully is frictionless. Until the monky grabs the pully him self. At which point I hope the rope will reach the ground with the bananas before it becomes tight. Other wise the monkey will tried to be pulled through the pully untill he lets go of it and balances it all out again.

[ori]

the puzzle did not mention the hihgt of the room.
If it is higher then 5, both bananas and monkey will be at the same hight, and at the same place - under the pulley, the shotest distance from the floor. the monkey will not climb at all for the bananas will be with him!
If it is lower than 5, then both babanas and monkey are on the floor. then the monkey won't climb either for he can just walk over to the bananas

[dumb]

I believe the monkey will move up and the bananas down...

[6000]

if the monkey tried to pull the rope it would make his side hevierso the bannanas would move up to the pully whole the monkey still would be in the same spot pulling until the bannanas stopped on the pulley and the monkey would pull himself up.

[HyToFry]

HAHA you insolent fools, i have tied a knot in our rope on both sides, right up near our pulley, NOW WHAT WILL HAPPEN..

to quote amb

bwahahahahah

[CrystyB]

This is posted only to have a reason for including some info on my topic. I'm sorry if you consider this to be unneeded.

quote:

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Ask The Minotaur
solution monkey business 3

Author Topic: solution monkey business 3
frankieg
Icarian Member posted 04-09-2000 08:10 AM
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by climbing the rope the weight will always remain equal meaning that as the monkey climbs the rope will shorten and eventually the bananas and the monkey will meet at the pulley.

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I do agree: by wanting to climb, the monkey has to apply some force to the rope. It is the action-reaction principle: if he DOES apply that force, the rope applies a counter-force that lifts the monkey. BUT the force applied to the rope is "traveling" around the pulley and lifts the bananas.

And if this ain't right, I still think the facts are as said, although i can't POSSIBLY prove it since i almoast didn't pass my physics exams all my high-school-life.

[Ghost Post]

mwf wrote:

"I will have to agree with Ori as long as the rope has no weight and the pully is frictionless. Until the monky grabs the pully him self. At which point I hope the rope will reach the ground with the bananas before it becomes tight. Other wise the monkey will tried to be pulled through the pully untill he lets go of it and balances it all out again."

Not if he's strong enough to hold back the weight. Considering he could pull
the weight of his own body, I think that's likely. :>

[G4]

one thing that no one has mentioned, that seems pretty important to me is -- the inertia of the pulley. If the the pulley has a lot of mass(and maybe some friction too) then the monkey could climb all the way to the top without the bananas moving at all(if he went slowly enough.)

Or maybe the pulley is very small.

I think this is the part of the puzzle that makes it too ambiguous to solve.

[OcularGold]

Sorry, i just realized im an idiot - the monkey will stay in place, since hes pulling down on the rope, it gets shorter, and the bananas will go up. The monkey does not go up.



[This message has been edited by OcularGold (edited 04-30-2000).]

[Ghost Post]

The only dynamic component is the climbing monkey. But the climbing itself has no effect on the balance of the system, as there are no external forces. The monkey and the bananas are always in balance; 1 KG on both sides!

The monkey will just get higher (the bananas will stay in place!) and will then reach the pulley.

This is true as long as the change in gravitational force and the air resistance can be neglected. Pulley friction and rope mass have no influence!

After reaching the pulley, he can hold it, apply an external force to the system and then haul in the bananas.

Bon appetit

ps. presuming the monkey is starving after having solved the problem, climbing 5 mtr. of rope and hauling in 1 KG of bananas.

[Jacob]

I have a monkey, some bananas, some rope and a pulley.
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The monkey ignores the rope and bananas and sits picking its nose.

[HyToFry]

Erik you said
"This is true as long as the change in gravitational force and the air resistance can be neglected. Pulley friction and rope mass have no influence!"

If gravity wasn't a factor, it wouldn't matter if the monkey weighed 500Kg, the bannans still wouldn't move (I don't think).

Also for some Reason i've noticed ALOT of ppl that think for some unknown reason that the monkey wants to get to the bannanas, minotaur never said the monkey did, for all we know it was a 1/2Kg monkey that was just force fed 1/2Kg of bananas.

[ori]

the question was
"IF the monkey tries to climb the rope, what will happen?"

my argument is that he won't climb at all. the position described in the question would be (graphically):
/@\
/ \
/ \
/ \
/ \
/ \
M B


the monkey can just reach out with one hand to get the bananas.

can't he?

[Ghost Post]

OK, I will state it more simple. A talked about "change in gravitational force", see my first try in this forum.

Secondly, you are right. The questions was: what will happen. Well that is simple: The monkey will go up.

Cheers

[Ghost Post]

And the bananas stay put!

[HyToFry]

He can, but ask yourself this, "Your a 1/2Kg monkey that was just force fed 1/2Kg of bananas, would you want to get your hands on the bananas, or would you be trying to get away from them by 'climbing' the roap?"

[HyToFry]

Only if the Pulley has infinate friction, of the rope has infinate mass .

[Tom]

Erik, why are you so convinced you are right, when everyone else thinks you are wrong?

And to everyone who talks about the monkey grabbing the bananas - no one said the monkey wants the bananas, they just said it climbs the rope .. forget about the bananas! Ori, you can't really ignore the bit after the "if" .. are you going to answer quetsion like "If I've got 3 lemons in one hand .. etc" with "But I don't believe you _do_ have 3 lemons!!!!"; "If a chicken takes 1 day to lay one egg .." "It doesn't!!!!!" etc etc

Well, now I've anoyed everybody, I'll shut up.

[This message has been edited by Tom (edited 05-05-2000).]

[smartiepants]

I think that if the monkey lets go of the rope at the same time that the hunter aims, then the bannanas will get across the river with Monty.

[Ghost Post]

I am not convinced I am right, I am trying to solve a puzzle.

Neither am I convinced that I am wrong, just because everybody says so (Columbus, and more recently Einstein, send their regards).
I do not compare myself with these blokes, but I have to state that here or somebody will critisize this remark.

Hey smartiepants.
First you presume that the monkey can see. Second, which hunter aims at what? Third, kidnapping of bananas is illegal. And fourth, with Monty I presume you mean the snake type?

Cheerio

Erik

[Tom]

Yeah, sorry Erik, I was in a bit of a bad mood when I wrote that. Just ignore it, please.

Didn't Columbus think he'd discovered .. erm .. Wales or something? And did Einstein meet with much opposition to his theories? But I happily concede the point you are making (though I still think the bananas go up)

[dr_mrr]

I solve Monkey III business in the following way.
Let the monkey climb up 1 metre on its side.Since the monkey and the banana bunch weigh the same,in the equilibrium position, there will be four and half metre rope on the side of bananas and five and half metre rope on the side of monkey,clinginging at four and half metre position below the pulley,leaving one metre of rope dangling free under the monkey.The next climb up of monkey by one metre will leave four metres of rope on the side of bananas and six metres of rope on the side of the monkey perching four feet below the pulley,leaving two metres of rope dangling free under it.Proceeding thus,it is clear that when the monkey climbs up ten metres on its side,it will meet the bunch of bananas at the top of the pulley.Of course,the pulley is assumed to be perfectly smooth,for otherwise,for some reason it is stuck up in the start,the monkey climb up all the five metres and the other side may not move at all !!!
M.R.Rangarajan

[Ghost Post]

Can somebody explain me the difference between the monkey hanging on the same level as the (now slowly rotten) bananas and a monkey hanging two meters higher than these (now almost black) fruits?

They still both weigh 1 KG and there is still the same length of rope on either side. So why would the bananas go up?

With this question I still ignore the change in gravitational force! Equilibrium says:
1KG of bananas on level 0 PLUS 1/2 rope equals monkey on level 2 PLUS 1/2 rope.

Where am I wrong?

[Tom]

I remember asking this exact question in the other thread about this damn monkey. You're right, the bananas won't magically rise to an "equilibrium" at the same height as the monkey. With the monkey and bananas at different heights, when the monkey climbs the bananas will rise at the same rate as the monkey, but the monkey will hit the pulley first.

But I'm not going to try to explain why; I've nothing to say that hasn't been said already (mostly in "monkey bidness")

[Ghost Post]

Erik: When the monkey pulls on the rope, why should the monkey go up, as opposed to the rope going down (on the monkey's side), so that the bananas go up?

Suppose the monkey and bananas are floating in space, with a rope stretched between them. If the monkey pulls on the rope, is he pullling himself toward the bananas, or is he pulling the bananas toward him? It's actually both. The same thing happens when they are suspended from a pulley.