Force: Gravity

Force_Gravity defines the acceleration due to gravity along the global X, Y, and Z directions.

<Force_Gravity

grav_x = "real"

grav_y = "real"

grav_z = "real" >

grav_x

Defines the acceleration due to gravity in the global X direction. The default value is 0.0.

grav_y

Defines the acceleration due to gravity in the global Y direction. The default value is 0.0.

grav_z

Defines the acceleration due to gravity in the global X direction. The default value is 0.0.

1.	grav_x, grav_y, grav_z may be specified as real numbers or as function expressions. This allows you to model gravity as a function of time. If gravity is modeled as a function of displacements, forces or other states of the system, MotionSolve may have difficulty finding a converged solution.

To represent state dependent gravity effects, use Force_Vector_TwoBody.

2.	The dimension of acceleration due gravity is: L T-2.

The example below shows the gravity components in SI units.

<Force_Gravity

grav_x = "0."

grav_y = "0."

grav_z = "-9810."

The following example shows gravity components modeled as a function of time.

grav_x = "9810*STEP(TIME,0,0,2,1)"

grav_y = "0."

grav_z = "-9810*STEP(TIME,0,1,2,0)"

Model Element
Description
ACCGRAV defines the acceleration due to gravity along the global X, Y, and Z directions.
Declaration
def ACCGRAV(IGRAV=0.0, JGRAV=0.0, KGRAV=0.0):
Attributes
IGRAV	Defines the acceleration due to gravity in the global X direction. The default value is 0.0.
JGRAV	Defines the acceleration due to gravity in the global Y direction. The default value is 0.0.
KGRAV	Defines the acceleration due to gravity in the global Z direction. The default value is 0.0.
Comments See Force_Gravity
Example The example below shows the default gravity components in mm/s/s. ACCGRAV(IGRAV=0.0,JGRAV=0.0,KGRAV=-9810.0)