         resultant = @forces.reduce (t, s) -> t.add(s)
         @applyForce(resultant, milliseconds)
         @forces = []
+        return this
 
     # Return true if this element intersects with the other
     # element, false otherwise.

        # Update the element's state.
        @setPosition(position)
        @setVelocity(velocity)

    # Apply the given forces to the element on the next step of the simulation.
    addForces : (forces...) ->

        return this if @isStatic()
        velocity = @getVelocity().add(impulse)
        @setVelocity(velocity)
        return this

    # Apply the given force to the element for the given number of
    # milliseconds.
