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Science project idea on why machines are not 100 per cent efficient.
Machine Efficiency Science Project Idea
Why machines are not 100 per cent efficient. Ideally, what should be the amount of work obtained from a machine as compared with the amount of work put in? For example, with a block and tackle, how many pounds should you be able to lift by an exertion of a force of 50 pounds? Actually, however, you will be able to lift not more than 60 or 75 per cent of this amount. In the same way you will find that the work obtained by the use of the inclined plane, cogwheels, etc., is not equal to the amount of work expended. This is due to the fact that there is a certain amount of resistance when one surface slides or rolls over another. This resistance, which is called friction, results because the surfaces are not absolutely smooth. Examination with the microscope will show that even the smoothest  appearing surface has many small irregularities. Naturally, therefore, when two surfaces rub together, what will happen?
 The efficiency of a machine is the ratio of the work done or energy given out to the work or energy put into it. For example, if in the block and tackle which we have considered before, we pull the power rope 6 feet with a force of 50 pounds and are able to lift a maximum weight of 200 pounds 1 foot, then the efficiency of the machine may be stated as follows:
Efficiency = work done (200 X 1) = 200 = 2 = 66 2/3
work put in (50X6) 300 3 After using the pulleys it will be found that they are slightly warmer. What, therefore, has become of energy that does not appear as useful work?
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