Тема: 33 psi
Definition: A pound-force per square inch (symbol: psi) is an imperial and US customary unit of pressure based on avoirdupois units. It is defined as the pressure that results when a force of one pound-force is applied to a one-square-inch area. One psi is approximately 6,895 pascals (N/m 2 ).
History/origin: Pound-force per square inch is a unit that originated in the imperial and US customary systems of units. It is based on the avoirdupois system, a system that uses weights in terms of the avoirdupois pound, which was standardized in 1959. The system is believed to have come into use in England around 1300 and was used in the international wool trade. As such, the prototype pound at the time was known as the avoirdupois wool pound.
