Force: Gravity

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

Format

<Force_Gravity

     grav_x = "real" 
    
     grav_y = "real"     

     grav_z = "real" >
/>

Attributes

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.

Example

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.

<Force_Gravity
     grav_x = "9810*STEP(TIME,0,0,2,1)"
     grav_y = "0."
     grav_z = "-9810*STEP(TIME,0,1,2,0)"
/>

Comments

  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.