1. Lecture 19 Satellites

2. Inflation The inflation rate in Zimbabwe is 213 million per cent. (Robert Mugabe) In Germany, after the first World War, their were postage stamps with denominations in the billions of marks.

3. Quick Review Newton’s Law of gravity

4. Circular Orbits M is mass of parent and m the mass of the satellite. M>>m Kepler’s Law

5. Geostationary Satellite At the equator, how far above the earth’s surface should a satellite orbit so it stays overhead? R earth = 6.37 x 10 6 m G=6.67 x 10 11 Nm 2 /kg 2 M earth = 5.98 x 10 24 kg

6. Homework due today 6: CQ1, CQ3, MC22, 1,2,4,7,9; WB: chapter 6: pages 6-5 and 6, exercises 13, 14

7. A cyclist goes around a level, circular track at constant speed. Since the cyclist’s speed is constant, her acceleration is constant 1.True 2.False

8. QUIZ A motor cycle is in a loop-the-loop. At the top of the loop… A) Draw a free body diagram B) What is the minimum speed the motor cycle must have if the radius of the loop is 15. m?

9. Problems Problem 6.1 6.4

10. Homework due Friday Problems: 6: 24, 25, 27, 29, 33, 44, 45, 51, 58, 59

11. Problem 6:27 What is the ratio between the sun’s gravitational force on you and the earth’s gravitational force on you? R earth = 6.37 x 10 6 m G=6.67 x 1011 Nm 2 /kg 2 M earth = 5.98 x 10 24 kg R earth-sun =1.5 x 10 11 m M sun = 1.99x10 30 kg

12. Problem 6:27 cont Take ratio

13. 6:33 The space shuttle is in an orbit 250 miles high. What are its orbital period (in minutes) and orbital speed? R earth = 6.37 x 10 6 m G=6.67 x 10 -11 Nm 2 /kg 2 M earth = 5.98 x 10 24 kg 1 mi = 1.609 km

14. 6:33 250 mi *1.609km/mi=326.5 km r= 6.37 x 10 6 m+3.265 x 10 5 m =6.70 x 10 6 T=5.46 x 10 3 s = 90.9 minutes

15. 6:44 A 5g coin is placed 15cm from the center of a turntable. µs = 0.80, µk = 0.50. As turntable starts from rest and speeds up to 60 rpm, does coin slide off?

16. So coin does not slip

17. T W=mg r=0.20m 1.0m θ 6:45 Conical Pendulum Find T, ω

18. 6:51 Ultracentrifuge R=0.10 m 70,000 rpm Δm= 10 mg = 0.000010 kg What is net force? r a

19. 6:58 Martian geostationary satellite What are its speed and altitude? dayMars:=24.8 hours

20. 6:59 g on Mars, Maximum walking speed?