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Author Topic: Simple Pulley Question  (Read 12530 times)
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Quest4PMD
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on: December 02, 2008, 11:07:10 pm » posted from:Bacoor,Cavite,Philippines



Can anybody help me?

I wanted to know how much force will be needed to rotate the big pulley (counter-clockwise) by 180 degrees. Please take note that there is a counter force of 1 kilo.


* pulley problem.jpg (40.89 KB, 878x465 - viewed 555 times.)
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lookang
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Reply #1 on: December 03, 2008, 02:50:59 pm » posted from:Singapore,,Singapore

i assume that a minimum force, F is required to initiate an acceleration clockwise by finding the force for balance.

By gear ratio,

F*(100) = F'(200) where F' is the equivalent force on the big gear on the right!


by principle of moment on the right gear,

total moment = 0

F'*200 = 1kN*(500)  ( i assume the kilo refers to kilo newton)
F(1/2)*200 =  1kN*(500)
F = 5 kN
therefore, minimum force required to set the system in motion is F > 5kN



Am i correct ?


the 180 degrees appears to be a trick question as once the system can move, the angular displacement will be achieved after some time.


you can model your simulation using EJS to engage in deep learning and you will learn a lot of stuff besides the answers to this question.

I welcome you to challenge yourself and immersed in a truly deep ICT tool for learning.  Grin

« Last Edit: December 03, 2008, 02:59:41 pm by lookang » Logged
Fu-Kwun Hwang
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Reply #2 on: December 03, 2008, 03:41:57 pm » posted from:Taipei,T'ai-pei,Taiwan

Because you only indicated that you want to rotate the big pulley by 180 degree.
But you did not say what is the rotating speed so the previous post show you how to calculate the minimum force.
For force large than minimum force, the pulley will have angular acceleration and you call calculate how much time for the system to rotate by 180 degree (But the pulley would not stop, it will continue rotating).

You should clearly indicate what you really want to do with the pulley system.
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Quest4PMD
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Reply #3 on: December 04, 2008, 04:24:35 am » posted from:Bacoor,Cavite,Philippines

Positively interesting! Thanks a lot to both of you for responding soon.

At the moment, I am only interested to know the minimum force required to set the system in motion. As I was dying to get a confirmation from experts like yourselves.

I will be using this info for the experiment I am conducting, some sort of a 'self-generating power generator'. Sounds absurd, right?

I am interested to use EJS, I'll check it out. Thanks again, I'm enlightened!
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