SettingsAutoClearForces Field

By default, forces are cleared automatically after each call to Step. The default behavior is modified with this setting. The purpose of this setting is to support sub-stepping. Sub-stepping is often used to maintain a fixed sized time step under a variable frame-rate. When you perform sub-stepping you should disable auto clearing of forces and instead call ClearForces after all sub-steps are complete in one pass of your game loop.

public const bool AutoClearForces = true