1. Chapter C13 Angular Momentum C13B.1, B.2, S.2 Due Wednesday

2. Monday – Review and problems Tuesday lab = conservation of angular momentum Wednesday - review Friday - Test over chapters C1-C14

3. Asteroid impacts (left over from chapter 12) The asteroid we think hit the Caribbean 65 million years ago and caused the extinction of the dinosaurs. Diameter of asteroid ~10 km Diameter of crater = 175 km Mass = 10 15 kg Velocity = 20 km/sec = 20,000 m/s. K.E. = ½mv 2 = 2 x 10 23 j An atomic bomb = 4 x 10 14 j

4. The atmosphere does not slow the asteroid at all. Immediately after impact the ejected material enters the hole punched in the atmosphere and the light produced is so bright it immediately ignites all material within 1000 miles. The whole Earth is showered with vaporized rock emitting a power 5 times that of the sun (catches many other things on fire.)

5. Holding rotating weights Is something conserved? Is that something K rot =½Iω ω 2 ? If K rot were conserved as the moment of inertia I increased, ω must decrease When measurements are made we find

6. Angular Momentum Angular Momentum =L= Iω Note that this is similar to linear momentum if I is m and ω is velocity. Linear momentum = mv So the conservation of angular momentum then becomes:

7. Other ways to write This is called a cross or a vector product.

8. Cross products The direction of r is perpendicular to the plane containing u and w and in a direction given by the right hand rule.

9. Cross product A B θ A=20 B=35 θ = 70º Find AxB.= 658 What is the direction of AxB? What is the direction of BxA?

10. Cross product Find C = A x B C = -31i-14j+5k Put on formula sheet.

11. Differences between dot and cross products of two vectors Dot or scalar product Answer is a scalar A∙B=ABcosθ Cross or vector product Answer is a vector Vector is perpendicular to A and B A x B=ABsinθ Direction is given by the right hand rule.

12. Problems due Wednesday C13B.1, B.2, S.2 Due Wednesday