1. Tuesday May 21

2. Overview Energy 1.Motion 2.Object 3.Potential 4.Mechanical Energy 5.Chemical 6.Elastic 7.Chemical 8.Gravitational 9.Elastic 10.Gravitational

3. The nature of energy 1.Energy of a spinning bicycle wheel 2.Energy stored in food 3.Energy stored in a boulder on a …. 4.Energy stored in a stretched string 5.Energy that is stored 6.Less 7.More 8.Energy 9.Joule 10.Potential,kinetic 11.Potential 12.Chemical

4. Chapter Test Continued 18)A 19)D 20)B 21)C 22)A 23)B 24)D 25)C Understanding Concepts 1.A. PE=mgh=10(9.8)(1.5)=147 J B. PE=mgh=(10)(9.8)(1)= 98 J 2. KE= ½ mv 2 =.5(10)(10)(10)= 500 J 3. KE=PE=147 J

5. There are two types of potential energy problems. A 4.5 kg dictionary sits on a 4.0 m high shelf. Find its potential energy. PE= mgh PE= 4.5 (9.8) 4 PE= 176.4 J A 12-N copper ball sits on a church stepple 40 m above the ground. Find its potential energy. PE=WH PE= 12(40) PE=480 J

6. An automobile to be transported by ship is raised 7.0 m above the dock. If its gravitational potential energy is 66000 J, find its mass. Given Solution

7. An automobile to be transported by ship is raised 7.0 m above the dock. If its gravitational potential energy is 66000 J, find its mass. Given H= 7.0 m A= 9.8 m/s/s PE= 66 000 J M= ? Solution PE=mgh M=PE/gh M= 66 000/9.8(7) M= 960 kg

8. The world record for pole vaulting is 6.15 m. If the athlete’s gravitational potential energy is 4,942 J, what is his mass? Given Solution

9. The world record for pole vaulting is 6.15 m. If the athlete’s gravitational potential energy is 4,942 J, what is his mass? Given H= 6.15 m PE= 4942 J G= 9.8 m/s/s M=? Solution PE=mgh M=PE/gh M= 4942/9.8(6.15) M= 82 kg

10. Find the kinetic energy of a.045 kg hockey puck traveling at 45 m/s. KE= ½ mv 2 KE= ½ (.045) (45)(45) KE= 45.56 J

11. A baseball is pitched with a speed of 35 m/s. Calculate its kinetic energy if it has a mass of 0.146 kg? Given Solution

12. A baseball is pitched with a speed of 35 m/s. Calculate its kinetic energy if it has a mass of 0.146 kg? Given M= 0.146 kg V= 35 m/s KE= ? Solution KE= ½ mv 2 KE= (.5)(0.146)(35)(35) KE= 89 J

13. A “ping-pong” ball has a mass of.00245 Kg and can be given a speed of 4.0 m/s. Find its kinetic energy? Given Solution

14. A “ping-pong” ball has a mass of.00245 Kg and can be given a speed of 4.0 m/s. Find its kinetic energy? Given M= 0.00245kg V= 4 m/s KE= ? Solution KE= ½ mv 2 KE= (.5)(0.00245)(4)(4) KE= 0.0196 J

15. Potential Energy Worksheet 1. PE=mgh or PE=WH 2. Joule (J) 3. PE=WH PE=12(21) PE=252 J

16. Potential Energy Worksheet 4. PE=WH PE=79(20) PE= 1580 J 5.PE=WH PE=190(45) PE=8550 J

17. Potential Energy Worksheet 6.PE=WH PE= 966(72) PE= 69, 552 J 7.PE=mgh PE=5(9.8)12) PE= 588 J

18. Kinetic and Potential Energy Worksheet 1 KE= ½ mv 2 KE= ½ 2.1(30*30) KE= 945 J 3 KE= ½ mv 2 KE= ½ (1120) 40 * 40 KE= 8,960,000 J

19. Kinetic and Potential Energy Worksheet 7.D 8.A 9.D 10.Friction.

20. Energy problems Worksheet 1. KE= ½ mv 2 KE= =.5(3) (5)(5) KE= 37.5 J

21. Energy problems Worksheet 2. PE=mgh PE= 6.5(9.8)(5) PE=166 J

22. Energy problems Worksheet KE= ½ mv 2 M= 2 KE/v2 M= 2(173)/(3.8 * 3.8) M= 24 J

23. Energy problems Worksheet PE=mgh H=PE/mg H=328/(7.5)(9.8) H=4.5m

24. Energy problems Worksheet 5. KE= ½ mv 2 KE= ½ 30 (2*2) KE= 60 J KE= ½ mv 2 KE= ½ 60 (2*2) KE= 120 J It doubles.

25. Energy problems Worksheet 6. KE= ½ mv 2 KE= ½ 30 (2*2) KE= 60 J KE= ½ mv 2 KE= ½ 30 (4*4) KE= 240 J It is quadrupled.

26. Energy problems Worksheet 7.PE= mgh PE= 4(9.8)(2) PE=78.4 J J PE=mgh PE= 4(9.8)(4) PE= 156.8 J It doubled.

27. Energy problems Worksheet 8. KE= ½ mv 2. 4.2 m/s KE= ½ 12 (3*3)

28. Energy problems Worksheet 9. KE= ½ mv 2 2KE= m (52*52) m= 72 kg

29. Energy problems Worksheet 10. PE= mgh PE= 0.49(9.8)(3.6) PE=17.3 J PE=mgh PE= 0.49(9.8)(1.5) PE= 7.2 J Decreased by 10.1 J