is a unit equal to a joule
multiplied by a second
, used to measure action
or angular momentum
. The joule-second is the unit used for Planck's constant
of a system has the dimensions of energy
integrated over time
; it is therefore measured in joule-seconds.
The angular momentum
of an object is the integral with respect to time of the torque
on the object. Torque in the SI system has the unit N
, so angular momentum has the unit N·m·s, or J·s.