1. 講者： 許永昌 老師 1

2. Contents A Little History Newton’s Law of Gravity Little g and Big G Gravitational Potential Energy Satellite Orbits and Energies 2

3. A Little History ( 請預讀 P385~P386) 3

4. Newton’s Law of Gravity ( 請預讀 P387~P391) Quiz: 4 2 1 2 1 (1) 2 1 (2)

5. Action (the motion of the moon) Purpose: Realize the motion of the moon. Action: Please calculate the ratio F earth on moon /F sun on moon. How about its motion? 5

6. Little g and Big G ( 請預讀 P391~P393) 6

7. Gravitational Potential Energy ( 請 預讀 P394~P395) 7 2 1 O

8. Exercise ( 請預讀 P396~P397) Since U=-GMm/r for universal gravitation, why can we write U g =mgy in Chapter 10? Hint: R E >>y, (Flat-earth approximation) 8

9. Satellite Orbits and Energies ( 請預 讀 P398~P402) 9

10. Exercise How to determine the mass of the sun from figure 13.18? It obeys log T = 1.500 log 10 r – 9.264. The height of the geosynchronous orbits. 10

11. Orbital Energetics 11

12. Orbital Energetics (continue) The condition of a Circular Motion 滿足不代表一定是 circular motion ，不滿足就一定是橢圓軌道。 Example: 1: 延切線推進，透過做功增加動能。 1  2: 利用 r 1 v 1 =r 2 v 2 與 E 1 =E 2 ，就可 求得 v 1 & v 2 。 (r 1, r 2 給定 ) 當然，實際上會複雜一點。 2: 增加動能，使之 E=  U g /2. 12

13. Homework Student Workbook 13.4, 13.6, 13.8 Student Textbook 13.20 13.29 13.54 13