Power

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Calculating Power

Power = work/time. If work is done quickly, more power is used. If work is done slowly, very little power is used. Power is measured in watts.

 For instance, if the same model airplane in the previous example expends 2.5 Joules in 2 seconds, the airplane will have expended 1.25 watts.

P

= W/T

 

= 2.5/2

 

=1.25 watts

In comparison, if the same airplane covers the same distance in 4 seconds, only 0.625 watts will have been used.

P

= W/T

 

= 2.5/4

 

= 0.625 watts

If two paper helicopters with the same mass are dropped from the same height, each will have done the same amount of work in reaching the floor. If, however, helicopter "A" falls faster than helicopter "B", then helicopter "A" will have used more power than the slower helicopter "B".

 

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