Power Formula
Power = Work ÷ Time
Let’s go back to that heavy rock you and your friend were moving across the yard. Let’s say it took you 4 seconds to move the rock 3 meters, using a force of 150 newtons. Remember from before that work = force x distance. How would you find out how much power the two of you put out?
Power = Work ÷ Time
Power = (150 newtons × 3 meters) ÷ 4 seconds
Power = 450 joules ÷ 4 seconds
Power = 112.5 joules/sec
Together, the two of you generated power of 112.5 joules per second as you pushed the rock across the yard.
Since power depends on both the work (which depends on force or strength) and the time it takes to do the work, when you think of a machine (including a person!) as powerful, the machine is both strong and fast. You may think you’re strong if you can lift a 100 lb sack of grain, and you are! If your little brother can only lift 25 lbs, but can lift four of them more quickly than you can lift your sack, then your brother is more powerful than you are.
Power
Solve the following: If it takes you 5 seconds to move a table 15 meters across the floor, using a force of 100 Newtons, how much power did you put out?
