Revolutions per minute velocity. The corresponding basic SI derived unit is s or Hz. When measuring angular speed, the unit radians per second is used. Formally, hertz (Hz) and radian per second (rad/s) are two different names for the same SI unit, s. However, they are used for two different but proportional ISQ quantities: frequency and angular frequency (angular speed, magnitude of angular velocity). The conversion between a frequency (measured in hertz) and an angular velocity (measured in radians per second) are: Thus a disc rotating at 60 rpm is said to be rotating at either 2 rad/s or 1 Hz, where the
Gray (unit) Gray (unit) The gray (symbol: Gy) is a derived unit of ionizing radiation dose in the International System of Units (SI). It is defined as the absorption of one joule of radiation energy per kilogram of matter. It is used as a unit of the radiation quantity absorbed dose which measures the energy deposited in a unit mass at a certain position, and of the radiation quantity kerma, which is the amount of energy that is transferred from photons to electrons per unit mass at a certain position. The corresponding cgs unit to the gray is the rad (equivalent to