Horsepower is usually calculated in the English system, (not necessarily in the world-wide metric system used in science and technology).
Before calculating horsepower, (HP); Work (W) must be found first. And W = Force x Distance, where force is measured in pounds, distance is measured in feet, and Work is measured in foot pounds.
The next step is to divide the Work by the Time; W/T = Power, where the quicker the work is done, the greater the power value will be. The label is in ft.lbs per second. Or ft.lbs/sec
One HP is equal to 550 ft.lbs per second, or 550 ft.lbs/sec. So, after calculating Power, a division by 550 ft.lbs./sec, will give the Horsepower or HP. The labels cancel out, and HP has no label other than it's value.
Example: A machine that moves 110 pounds, a distance of 20 feet produces 2200 ft.lbs. of Work. If the machine can do this task in 2 seconds, then the Power of the machine is 1100 ft.lbs.per second. Divide the Power by 550 ft.lbs.per second, and the HP for the machine is 2.
Two students volunteer in class to have their horsepower calculated. The data collected comes from each of them being timed after running up the same double flight of stairs. Each flight is 20 ft. in total distance, plus an 8' 9” flat landing located between the two flights.
Tiny Ted weighs 78 lbs. while Big Ben weighs 312 lbs. Ben's time to run the whole distance is 7.9 seconds.
1.Calculate: 1.a, Big Ben's work, 1b, his power, 1c, his Horsepower
2.a, Calculate Tiny Ted's Work, 2.b, How fast must Tiny Tim run the stairs in order to tie or beat Ben in Horsepower? (Rounding to a 10th of a second is permissible) 2.c, Is Tiny Ted's time a realistic possibility?