WORK AND EFFICIENCY. WHAT IS WORK? Definition:  The use of force to move an object Not all force used to move an object does work The force must be applied.

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Presentation transcript:

WORK AND EFFICIENCY

WHAT IS WORK? Definition:  The use of force to move an object Not all force used to move an object does work The force must be applied in the same direction that the object moves

CALCULATING WORK Work is directly related to both the force applied to an object and the distance the object moves Work = Force X Distance Unit for work = joule (J)

EFFICIENCY All machines make work easier but they don’t increase the amount of work that is done All machines have friction Amount of work needed to overcome friction in a machine depends on the machine’s efficiency User always does more work on the machine than the machine does on the object Mechanical efficiency is always less than 100% Closer to 100% the better the machine is at reducing friction

CALCULATING EFFICIENCY Efficiency can be calculated with the equation: Practice: A machine puts out 6000 joules of work. To produce that much work from the machine requires the user to put in 8000 joules of work. What is the efficiency of the machine? 6000J/8000J x100% = 75%