Physics (9PH01) 1.2 Unit 4: Physics on the Move Circular motion Centripetal Acceleration 1. The rate of change of velocity is called as centripetal acceleration, a c . Diagram 1 , ∆v Diagram 2 Change of speed 2. From diagram 1, the linear velocity v A and vB are equal magnitude but different direction. 3. Consider vector diagram in diagram 2, let RQ and PQ represent the magnitudes and direction of v A and vB respectively, the change of velocity, ∆v = v B − v A = PQ − RQ = PQ + QR = PR 4. When ∠PQR is small, we approximate that the direction of PR is toward the centre of the circle, O . ∆v PR 5. Hence, acceleration, a = = ∆t ∆t 6. Consider ∆PQR , if ∠PQR is small, then PR ≈ v∆θ a= ∆θ PR v∆θ = = vω since ω = ∆t ∆t ∆t v2 = rω 2 ac = vω = r Reference: Advanced Level Physics, 7th Edition, Nelkon and Parker.