Horse power

Horse power Horse" pow`er 1. The power which a horse exerts. [1913 Webster]

2. (Mach.) A unit of power, used in stating the power required to drive machinery, and in estimating the capabilities of animals or steam engines and other prime movers for doing work. It is the power required for the performance of work at the rate of 33,000 English units of work per minute; hence, it is the power that must be exerted in lifting 33,000 pounds at the rate of one foot per minute, or 550 pounds at the rate of one foot per second, or 55 pounds at the rate of ten feet per second, etc. [1913 Webster]

Note: The power of a draught horse, of average strength, working eight hours per day, is about four fifths of a standard horse power. [1913 Webster]

{Brake horse power}, the net effective power of a prime mover, as a steam engine, water wheel, etc., in horse powers, as shown by a friction brake. See {Friction brake}, under {Friction}.

{Indicated horse power}, the power exerted in the cylinder of an engine, stated in horse powers, estimated from the diameter and speed of the piston, and the mean effective pressure upon it as shown by an indicator. See {Indicator}.

{Nominal horse power} (Steam Engine), a term still sometimes used in England to express certain proportions of cylinder, but having no value as a standard of measurement. [1913 Webster]

3. A machine worked by a horse, for driving other machinery; a horse motor. [1913 Webster]