Allows scaling of the force that is applied when the effector attempts to attain the specified speed along the surface. If 0 then no force is applied is is effectively disabled. If 1 then the full force is applied. It can be thought of as how fast the target object is modified to meet the specified speed with lower values being slower and higher values being quicker. Care should be taken however as applying the full force will easily counteract any other forces being applied to the target object such as jump or other movement forces. For this reason, a value less than 1 is advised.