horsepower

/hawrs"pow'euhr/, n.
1. a foot-pound-second unit of power, equivalent to 550 foot-pounds per second, or 745.7 watts.
2. Informal. the capacity to achieve or produce; strength or talent: The university's history faculty is noted for its intellectual horsepower.
[1800-10; HORSE + POWER]

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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.

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▪ unit of measurement
      the common unit of power; i.e., the rate at which work is done. In the British Imperial System, one horsepower equals 33,000 foot-pounds of work per minute—that is, the power necessary to lift a total mass of 33,000 pounds one foot in one minute. This value was adopted by the Scottish engineer James Watt (Watt, James) in the late 18th century, after experiments with strong dray horses, and is actually about 50 percent more than the rate that an average horse can sustain for a working day. The electrical equivalent of one horsepower is 746 watts in the International System of Units (SI), and the heat equivalent is 2,545 BTU (British Thermal Units (British thermal unit)) per hour. Another unit of power is the metric horsepower, which equals 4,500 kilogram-metres per minute (32,549 foot-pounds per minute), or 0.9863 horsepower.

      Horsepower at the output shaft of an engine, turbine, or motor is termed brake horsepower or shaft horsepower, depending on what kind of instrument is used to measure it. Horsepower of reciprocating engines, particularly in the larger sizes, is often expressed as indicated horsepower, which is determined from the pressure in the cylinders. Brake or shaft horsepower is less than indicated horsepower by the amount of power lost to friction within the engine itself, which may amount to 10 percent or more of the indicated horsepower. Electric motor horsepower can be determined from the electrical input in watts, allowing for heat and friction losses in the motor itself. Thrust horsepower of jet engines and rockets is equal to the thrust in pounds force times the speed of the vehicle in miles per hour divided by 375 (which is equal to one horsepower measured in mile-pounds per hour).

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Universalium. 2010.

Look at other dictionaries:

  • horsepower — [hôrs′pou΄ər] n. [first adopted by WATT James] 1. the power exerted by a horse in pulling pl. horsepower 2. a basic unit of power in the FPS system, equal to the power needed to raise a weight of 550 pounds a distance of 1 foot in 1 second or a… …   English World dictionary

  • horsepower — horse‧pow‧er [ˈhɔːsˌpaʊə ǁ ˈhɔːrsˌpaʊr] written abbreviation hp noun [countable, uncountable] a unit for measuring the power of an engine: • The test vehicle s horsepower was increased by 11% …   Financial and business terms

  • horsepower — 1806, from HORSE (Cf. horse) + POWER (Cf. power); established by Watt as the power needed to lift 33,000 pounds one foot in one minute, which is actually about 1.5 times the power of a strong horse …   Etymology dictionary

  • horsepower — ► NOUN (pl. same) ▪ an imperial unit of power equal to 550 foot pounds per second (about 750 watts), especially as a measurement of engine power …   English terms dictionary

  • Horsepower — hp redirects here. For other uses, see HP (disambiguation). Horsepower (HP) is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.[1] Horsepower was originally defined to compare the… …   Wikipedia

  • horsepower — (HP) A measurement of the engine s ability to perform work. One horsepower is defined as the ability to lift 33,000 pounds one foot in one minute. To find horsepower, the total rate of work in foot pounds accomplished is divided by 33,000. If a… …   Dictionary of automotive terms

  • Horsepower — Einheit Norm Alte Maße und Gewichte Einheitenname Pferdestärke Einheitenzeichen PS Beschriebene Größe(n) Leistung Größensymbol(e) …   Deutsch Wikipedia

  • horsepower — (hp)    a unit of power representing the power exerted by a horse in pulling. The horsepower was defined by James Watt (1736 1819), the inventor of the steam engine, who determined after careful measurements that a horse is typically capable of a …   Dictionary of units of measurement

  • horsepower — noun /ˈhɔː(r)spaʊə(r)/ a) A non metric unit of power (symbol hp) with various definitions, for different applications. The most common of them is probably the mechanical horsepower, approximately equal to 745.7 watts. political horsepower b) A… …   Wiktionary

  • Horsepower — Horse|pow|er auch: Horse|po|wer 〈[hɔ:spaʊə(r)] f.; , ; ; in angelsächsischen Ländern〉 Einheit der Leistung, 1 h.p. = 1,013 PS = 745,7 W [engl., „Pferdestärke“] * * * Horse|po|w|er [ hɔ:spaʊə ], die; , [engl. horsepower, eigtl. = Pferdekraft]… …   Universal-Lexikon

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