Define efficiency of a simple machine? Do you think that in actual practice the efficiency of a machine is 100°/•? If not, explain the reason?

Explanation:

Part 1 :

The efficiency of a simple machine is defined as the ratio of useful work done by the machine ( output work ) to the total work put into the machine ( input work ).

Part 2 :

In practice , the work output of a machine is always less than the work input due to the effect of friction. Since, there is always some loss of energy in the machine , if the frictional force in machines increases , efficiency decreases. Because machines are not frictionless in practice , efficiency of a machine is never 100% or greater.

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the answer is a 3.8cm

explanation:

answer would be letter choice (a),   a ball resting on a shelf. would be another example of potential energy   >   stored energy > not moving.

a ball spinning on a finger   >   kinetic energy > moving energy

a ball rolling on the ground   >   kinetic energy   > moving energy

a   ball flying through the air   > kinetic energy   >   moving energy

hope that                                         : )