Stationary reference system, with X axis horizontal and positive to the right, and Y axis vertical an positive to upwards.
|g:||Value of the gravity (absolute value). To default write the gravity value to the selected system (9.81 m/s2 to SI, and 32.2 ft/s2 to English system).|
|t:||Time of the problem, to be used in data of power and momentum. To default writes 1, to avoid a power undefined data.|