1. Warm Up  1) Define Acceleration  2) If a bike goes in a circle traveling at 10 m/s is it accelerating?  3) What is Newton’s second Law?

2. Go over Quiz

3. Acceleration  Acceleration is a change in velocity.  a is a vector, so a change in direction is also a change in acceleration. Not just a change in speedNot just a change in speed

4. Centripetal Acceleration  An object, going in a circle (or part of a circle) at constant speed IS accelerating  Called centripetal acceleration a ca c a c = v 2 /ra c = v 2 /r

5. Example  A confused mouse runs in a circle with a constant speed of 3 m/s. If the mouse’s circle has a radius of 5 m, what is the acceleration of the mouse?

6. Practice  A cyclist bikes in a circle with radius 2000 m at a constant speed of 20 m/s. What is the cyclist’s acceleration?

7. Centripetal Force  F = m*a (Newton’s 2 nd law) soooooo  F c = m * a c  F c = m * (v 2 /r) ‏  What direction should this force go? Make a picture (FBD) ‏Make a picture (FBD) ‏

8. Example  A confused mouse (mass 0.2 kg) runs in a circle with a constant speed of 3 m/s. If the mouse’s circle has a radius of 5 m, what is the magnitude of the force turning the mouse in a circle?

9. Practice  A cyclist (mass 100 kg) bikes in a circle with radius 2000 m at a constant speed of 20 m/s. What is the magnitude of the force turning the cyclist?

10. Homework Pg 129 (Q1-3, 5-6; P 1, 2, 4) ‏