how are the horse power units messured, and how does it differ from the real power of a horse?

Question

thats a stupid question but its interesting

Answer 1

Common unit of power, the rate at which work is done. In the English system, one horsepower equals 33,000 foot-pounds of work per minute — that is, the power necessary to lift a total of 33,000 lbs a distance of one foot in one minute. This value was adopted by James Watt in the late 18th century after experiments with strong dray horses and is actually about 50% more than the rate an average horse can sustain for a working day. The electrical equivalent of one horsepower is 746 watts in the International System of Units; the heat equivalent is 2,545 BTU per hour. The metric horsepower (see metric system) equals 4,500 kg-m per minute (32,549 foot-pounds per minute), or 0.9863 horsepower.

Answer 2

Horsepower is actually derived from the amount of work a horse could do under test conditions. A certain type of horse was chosen to lift 1000 pounds 10 ft vertically with a rope through a pulley. The horse performed this work a certain number of times. Each pull was timed. By this method it was found that the work this horse could do over time was equal to 550 ft. lbs/sec. Early in the 20th century this became a standard for measuring work.

Answer 3

Horsepower is a unit of power (like the watt). It is equal to 33,000 ft·lbs per minute in most applications.

An article in Nature in 1993 calculatied the upper limit to a horse's power output. The peak power over a few seconds has been measured to be as high as 14.9 Hp. However, for longer periods an average horse produces less than one horsepower.
http://en.wikipedia.org/wiki/Horsepower#Horsepower_from_a_horse

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