1. June 9, 2009 Bluff

2. What are the units for: work, power, energy? Work = joule (J) Power = watt (W) Energy = joule (J)

3. What is the power exerted when 3000 mJ of work is done in 2 s? P = W t W = 3000 mJ x 1 J - 1000 mJ P = 3 J = 1.5 W 2 s

4. How much work is done when a 320 N box is pushed 6 m? W = F x d W = (320 N) x (6 m) W = 1920 J

5. What type of energy is food? What is it transformed into after you eat it? Chemical Potential and kinetic

6. Why are machines not 100% efficient? Friction causes energy to be “lost” as heat (thermal energy)

7. What is the potential energy of a 5 N object that is 3 m off the ground? PE = w x h PE = (5 N) x (3 m) PE = 15 J

8. What is the mass of an object with 5 kJ of potential energy at a height of 25 m? m = PE - (g x h) PE = 5 kJ x 1000 J = 5000 J 1 kJ m = (5000 J) = -20.4 kg (9.8 m/s 2 x 25 m)

9. Name a device that transforms electrical energy into useful heat energy. Hair dryer Toaster Heater

10. Name a device that turns chemical energy into mechanical energy. Car Toys with batteries Battery powered fans Your body (food!)

11. Name an object that converts chemical energy into light energy. Flashlight Glowstick Headlights of car

12. What must be true about the energy into a chemical reaction and the energy out of a chemical reaction? They must be equal! LAW OF CONSERVATION OF ENERGY!

13. A dog with a mass of 3000 kg sits at the top of a 5 m hill. If the dog has 150 kJ of potential energy, what is the potential energy halfway down the hill? New PE = initial PE 2 New PE = 150 kJ 2 New PE = 75 kJ

14. What happens to the sum of potential and kinetic energy as the skater moves on the track? Stays the same Law of conservation of energy!

15. At what point is the potential energy the greatest? The least? A B C D E Greatest: A Least: B A

16. Which point(s) have less kinetic energy than point C? A & E A B C D E

17. If 500 J of work is put into a system and 330 J is released as light, how much was “lost” to friction? 500 J – 330 J = 170 J

18. Normally, which type of wave travels slowest? Sound

19. If a wave travels at 331 m/s and has a frequency of 6.5 Hz, what is the wavelength? λ = V f λ = 331 m/s 6.5 Hz λ = 50.9 m

20. A wave with a frequency of 2 Hz and a wavelength of 5000 nm is traveling at what speed? V = λ x f V = (5000 nm) x (2 Hz) V = 10,000 nm/s

21. Define refraction. When a wave moves into a different medium, changes speed, and bends

22. What are two differences between destructive and constructive interference? Destructive- overlap of crest/trough; causes decrease in amplitude Constructive- overlap of 2 same things; causes increase in amplitude Waves must be traveling toward each other!

23. What type of wave is shown below? What’s an everyday example of this type of wave? Transverse light A B C

24. A B C Which letter represents the amplitude of the wave? B

25. Which letter represents the wavelength of the wave? A A B C

26. If the wave travels in 4 sec, what is the frequency? f = cycles t f = 2 cycles 4 s f = 0.5 Hz A B C

27. If the pitch of the sound gets lower, what happened to the wave? The frequency decreased

28. If you turn up the volume on your stereo, what happened to the wave? The amplitude increased

29. When a sound wave moves from air into the wall, what happened to the speed of the wave? It increased

30. Which wave shown below is a sound wave? What is the name of this type of wave? the top one Longitudinal (compression, pressure)

31. Complete the statement: Waves carry _____, not _____ from one place to another. (hint: fishing bobber) Waves carry ENERGY not MATTER from one place to another

32. What makes something echo? Reflection of sound wave

33. Define reflection When wave hits a surface and bounces back

34. What type of electromagnetic wave has the greatest amount of energy? Gamma

35. What type of electromagnetic wave has the longest wavelength? Radio

36. What color has the lowest frequency? Red

37. Thunder is heard _____ lightning strikes because____________. Thunder is heard AFTER lightning strikes because sound travels slower than light.

38. Which electromagnetic waves are mostly responsible for skin cancer, sunburn, and cataracts? Ultraviolet

39. Why are RADIO messages delayed when we send a message to astronauts on the moon? GREAT distance

40. What type of wave is emitted (given off) by the sun? Ultraviolet

41. Define current Charges flowing thru a circuit

42. Define resistance Opposes (goes against) the flow of electrons

43. Can a neutral object be attracted to a positive object? If so, how? If not, why? (Hint: think balloon and wall) Yes- the charges in the neutral objects can be rearranged

44. When you rub a balloon on your hair, what’s happening with the charges? Electrons (negative) are moving from hair to balloon, causing balloon to have an excess charge (too much)

45. What are two differences between a parallel and series circuit? Parallel- more than one option for e- travel, one bulb out doesn’t ruin the entire circuit (looks like a ladder) Series- only one path for e- travel, one bulb out means all out (one big circle)

46. If you double the charge of one object, what happens to the force between them? Increases by 2 –2 x 1

47. If you cut the charges of both objects by ½, what happens to the force between them? Decreases to ¼ (½ x ½) Decreases by 4

48. If you cut the distance between two objects to ¼, what happens to the force between them? Increases by 16 –(¼) 2 = 1/16, then inverse!

49. If you double the distance between two objects, what happens to the force between them? Decrease by 4 Decrease to ¼ –2 2 = 4, Inverse!