What is one horse-power?
In physics and engineering, the terms ‘work’ and ‘energy’ are equivalent: in the Systme Internationale (SI) their unit of measure is named after the physicist James Joule (1818-1889) as the joule. One horse-power (1 hp) is the Imperial measure of the rate at which work is done or energy is expended. It is roughly that which can be achieved by a standard shire-horse. The SI unit of power is named after the inventor of the condensing steam engine James Watt (1736 – 1819) as the watt. If a force enough to accelerate a one kilogramme-weighted object (1 kg) by one metre per second (1 m s-1) in one second (1 s) is applied then one watt (1 W) of power is required or one joule (1 j) of work is done in 1 s. The joule and watt are, therefore, derived units: they are related to the more fundamental units of Mass (kg) Length (m) and Time (s) by: 1 joule = 1 kg m2 s-2 (Read as: One joule equates to one kilogramme metre squared per second squared) 1 watt = 1 kg m2 s-3 = 1 j s-1 (One watt equates to
