EXERCISE 66 

 WHAT IS THE EFFICIENCY OF A PULLEY SYSTEM? 



Materials. Data from the two preceding exercises. 



Directions. Secure from the two preceding exercises the following data : 



What percentage of the work in is secured in work out ? Under what conditions could work out 

 equal work in ? What would be the percentage of efficiency when work out equals work in ? 



Additional problems. How do you account for the fact that the amount of work done upon a pulley 

 system is greater than the amount of work secured from it ? What becomes of the work wasted ? 



Is it possible to construct a machine from which as much work or more work may be secured than 

 the amount of work put into it ? Do you know of any such machines ? 



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