1. Centripetal acceleration What is it? –The acceleration of a mass moving in a circle at constant (?) angular velocity. OK, so how can we have an acceleration with a constant angular velocity????? Remember acceleration is change in velocity per time. Velocity is a vector!

2. Centripetal Acceleration Velocity is a vector, so it has… –Magnitude (speed), (how fast, m/s, mph, etc) –Direction, (where are you going, N, S, E, W etc) Acceleration is changing velocity with time. –Change speed, faster or slower. –Or…change direction, keeping speed constant

3. Centripetal Acceleration

4. Derivation a centripetal v tangential t r r What’s this distance?

5. Centripetal Acceleration Derivation v t t acac r r d=? …goes something like this… Right triangle, pythagorean theorem, For instantaneous acceleration, let  t get way small, d gets way smaller that 2r

6. Centripetal Acceleration Derivation v t t acac r r

7. So what do you gotta know…

8. Just kidding Just this!

9. Let’s try some. What is the centripetal acceleration of a rock stuck in the tread of my.45 meter radius tire while is spins at 50 rad/sec?

10. Ok, another! What causes the centripetal force that holds the rock in my tire? The rock has a mass of 0.020 kg. What is its value of the centripetal force?