1.The blade of a windshield wiper moves through an angle of 90 degrees in .28 . The tip of the blade moves on the arc of a circle that has a radius .76m. What is the magnitude of the centripetal acceleration at the tip of the blade. 2. Ac= v^2/r 3. okay, the accleration should equal r(theta)/t but whenever I plug in my variables and solve I get an answer in the 7000s which is not reasonable at all. The actual answer is 24 m/s^2 but I have no idea how to get there.