public Boolean Remove(CompositePhysicalObject obj)
 {
     if (obj != null && objectList.Contains(obj))
     {
         objectList.Remove(obj);
         return true;
     }
     return false;
 }
 public Boolean Add(CompositePhysicalObject obj)
 {
     if (obj != null && !objectList.Contains(obj))
     {
         objectList.Add(obj);
         return true;
     }
     return false;
 }