code: def force(self,c):
          '''control force plus the external forces (drag, etc)'''
          
          # bring instance variables into local scope
          x = self.x
          v = self.v
          b = self.b
          k = self.k
          x0 = self.x0
          
          F = self.control_force(c)
          
          return F - b*v - k*(x - x0f force(self,c):
          '''control force plus the external forces (drag, etc)'''
          
          # bring instance variables into local scope
          x = self.x
          v = self.v
          b = self.b
          k = self.k
          x0 = self.x0
          
          F = self.control_force(c)
          
          return F - b*v - k*(x - x0)
docs: control force plus the external forces (drag, etc)