To Enter External Load Information
Use the External loads tab to specify external loads information for dynamic, static, and force balance analysis types. You cannot set an external load for position and kinematic analyses.
By default, all external loads in the model at the time that you define the analysis are included in the analysis. To include external loads created after completing the analysis definition, click 
to explicitly include them.
to explicitly include them.If you click the name of any load in the list, you can select another load. Use this method to choose more than one instance of an external load, where the instances are active for different times in an analysis.
Keep the following considerations in mind when entering external load information:
• From and To times
◦ All external forces are active by default from Start to End of the analysis.
◦ You can select the Start and End times from the list or specify a numeric value for a dynamic analysis.
◦ You cannot apply Start and End times for static and force balance analyses.
◦ The validation check initiated by the OK or Run command resets any inappropriate values to the Start or End values.
• The Enable gravity check box is not selected by default. Gravity is zero if the check box is not selected.
• The Enable all friction check box is not selected by default. No friction is applied if the check box is not selected.