   damping: 0.9999 # minimal
   angularDamping: 0.9999
 
+  # bookkeeping
+  lastAcceleration: [0, 0]
+
   vertices: -> []
 
   color: "#CCC"

      # TODO add forces here from whatever external forces are present (force
      # generators + force generator registry?)

      @velocity = Vec.scale @velocity, Math.pow(@damping, dt)
      @velocity = Vec.add @velocity, Vec.scale @acceleration, dt

    if @inverseMoment > 0
      @orientation = Rotation.addAngle @orientation, @angularVelocity * dt

    @velocity = opts.velocity or @velocity
    @angularVelocity = opts.angularVelocity or @angularVelocity

    @acceleration = opts.acceleration or @acceleration

    @calculatePhysicalProperties opts

  reset: ->
