Efficiency of Pulley System for Finals | Help Needed!

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Homework Help Overview

The discussion revolves around determining the efficiency of a pulley system in a physics context. The original poster seeks assistance with a problem involving the work required to lift a box using a pulley, specifically asking for the formula and examples related to efficiency calculations.

Discussion Character

  • Exploratory, Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the relationship between work input and output, with one suggesting a formula for efficiency. There is also a question regarding potential discrepancies in problem parameters, such as the input work value.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem and questioning the values provided. Some guidance on the formula for efficiency has been offered, but there is no consensus on the correct input values or the resulting efficiency calculation.

Contextual Notes

Participants note differences in academic schedules and terminology, indicating potential variations in educational contexts. The original poster expresses constraints due to access to resources and time pressure from upcoming finals.

SummerSweety30
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HELP for finals PLEASE!

Can someone please quickly tell me how to determine the efficiency of this stupid pulley? I'm so lost :confused: at how to do it and finals are next week. Our set of books for our Principles of Technology class have to stay in the room and my teacher is grading the binder that has all my work in it! I've done most of the review on my own but I'm lost at what to do in these word problems... HELP! Here it is... Email me if you can...
Crystal

Find the efficiency of a pulley system that requires 30 Nm of work to life a 5kg box to a height of 3 m.

:bugeye:
I don't have to have the answer... If someone could post an example that would be great but I really just need to know the formula of how to do it. I'll post more as I need help... Thanks so much!
 
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I am thinking that since W = Fx = mgh so...
(5*9.8*3)/90 = 1.67
 
Hey hey hey

But how did you get that? our terms might be different because it says your in australia and I'm in Texas but still... Whats the formula..? I got to know it to take the tests you know? Thanks though... THats amazing...

Crystal
 
SummerSweety30 said:
Find the efficiency of a pulley system that requires 30 Nm of work to life a 5kg box to a height of 3 m.
The efficiency of a simple machine is defined as [work out]/[work in] X 100. The highest efficiency possible is 100 percent, if there is no friction, etc. I suspect you have a typo in your problem statement, since your numbers will give:
work output: mgh = 5 (9.8) 3 = 157 Nm
work input: 30 Nm

so: efficiency = 157/30 x 100 = 523 % ! :bugeye:
I don't think so... (Perhaps the work input was 300 Nm?)
 
i know this is offtopic but how dou have finals in december? when does the academic year start for u guys?
 
hi

I live in Texas over in the U.S. We have finals all next week... Then we have christmas break until January... Later

Crystal
 
Same here in college in quebec. We are finishing our first session with a week of exams
 

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