 The centripetal acceleration given by formula_13 is normal to the arc and inward.When the particle passes the connection of pieces, it experiences a jump-discontinuity in acceleration given by formula_13, and it undergoes a jerk that can be modeled by a Dirac delta, scaled to the jump-discontinuity.For a more tangible example of discontinuous acceleration, consider an ideal spring-mass system with the mass oscillating on an idealized surface with friction.