1. 講者： 許永昌 老師 1

2. Contents A “Natural Money” called Energy 但是， money 事實上是 “ 無定的 ” 。 Kinetic Energy and Gravitational Potential Energy Elastic Force and Elastic Potential Energy Elastic Collisions Energy Diagrams Molecular Bonds 2

3. A “Natural Money” called Energy ( 請 預讀 P267~P268) 3 Key Points: Transform: L 與 S 可互相交換而不會 損失, i.e. L+S=W, W is a constant. Transfer: Income I & Expenditure E Before  After (for system) W i (I & E) W f =W i +I  E

4. Kinetic Energy and Gravitational Potential Energy ( 請預讀 P269~P277) 4 F net N v, dr FGFG

5. Exercises Energy bar chart for a ball slide down a slides A block slides down a frictionless ramp of height h. It reaches velocity v at the bottom. To reach a velocity of 2v, the block would need to slide down a ramp of height a. 1.41h b. 2h c. 3h d. 4h e. 6h 5 h 1. y=0 m 2. y=0 m

6. Law of Conservation of Mechanical Energy ( 請預讀 P277) 6 E=K+UE=K+U Energy into systemEnergy out of system ( 千萬不要用背的，因為它是有條件的 )

7. Homework Student Workbook 10.1 10.2 10.3 10.4 10.6 7

8. Summary I Law of Conservation of Mechanical Energy 8 E=K+UE=K+U Energy into systemEnergy out of system

9. Action: spring ( 請預讀 P278~P284) Purpose: The significance of spring constant. The mathematical formula of a spring force. Actors and Objects: One student. Two springs. Actions: How would you characterize the difference of the springs? The mathematical formula of the spring force. 9

10. Spring forces 10 0 xexe x C B EE as if

11. Elastic Potential Energy ( 請預讀 P280~P284) Situation: The elastic potential energy for a ball attached to a spring. System: ball Elastic Potential energy: U= ½ k  x 2. Because: Energy bar chart: 11 0 xexe x 0

12. Exercises Ex.10.15 You need to make a spring scale for measuring mass. You want each 1.0 cm length along the scale to correspond to a mass difference of 100 g. What should be the value of the spring constant? Compare the compressed length of these two situations: A 10 kg runaway grocery cart runs into a spring with spring constant 250 N/m and compresses it by 60 cm. What was the speed of the cart just before it hit the spring? 12 Wall

13. Homework Student Workbook 10.10 10.11 10.12 10.13 10.15 10.16 13

14. Summary II 14 C B as if

15. Elastic Collisions ( 請預讀 P284~P288) 15 12

16. Elastic Collisions For 1D elastic collision: Conditions: m 1 v 1xi +m 2 v 2xi =m 1 v 1xf +m 2 v 2xf ½m 1 v 2 1xi + ½m 2 v 2 2xi = ½m 1 v 2 1xf + ½m 2 v 2 2xf Solve: 16 ( 請自己推一次， 我就不在課堂推了 ) ( 請自己推一次， 我就不在課堂推了 )

17. Homework Student Workbook 10.17 17

18. Energy diagrams ( 請預讀 P288~P291) 18

19. Action: Energy Diagram Purpose: Get the quantities from an energy diagram Turning points: (?=0) Stable equilibrium (?=0, ??>0) Unstable equilibrium (?=0, ??<0) The speeds. Actions: When TE=1 J, … When TE=2 J, … When TE=2.5 J, … Plot its Kinetic energy versus x graph when TE=2.5 J. 19 (PE) E (J) x (m)

20. Homework Student Workbook P10-7~P10-8 Textbook 10.17 10.31 10.38 10.42 10.53 10.60 一樣，請將 terms and notation 製作成名詞卡片。 20