ANSWERS to PRACTICE TESTS!

[wafisher]

U12A Static Electricity

NOTE! Pay attention to significant figures!

1 Potential Difference = 9200 V
2 F = 4.0e-16 N
3 q = 1.6e-3 C
4 W = 5.6 J
5 E (electric field intensity) = 700 N/C

6 Potential Difference = 1220 V
7 q = 0.223 C
8 E = 1.7e+5 N/C
9 F = 7.4 N to the left (harder problem! use vectors to solve for net force)
10 6.25e+18 electronc

11 f = 4f (increases 4x)
12 q = 0.030 C
13 d = 0.019 meters
14 F = 2.9 N

[jinjin]

this is weird... i actually understand this stuff now and even got the hardest question right!! and guess what #9 the really confusing one was the same one on the glencoe quiz!!! me and will did it and we got it right...lets do more glencoe quizzes..it actually helps!! ;D

[wafisher]

Practice Test - Work and Energy 2006

Check your answers and give me a score!

1. W = 3.3 J
2. W = 1070 J
3. W = 8.55 x 10^7 J
4. W = 4400 J
5. W = 80,000 J

6. P = 46,000 watts
7. Work done by adult = 8200 J
Work done by child = 4100 J
8. W = 41 J
9. 586 g pot has 8.61 J of potential energy
other pot has 8.50 J of potential energy
10. v = 3.7 m/s

11. d = 4.5 m
12. loss = 6.1 J
13a. W = 240, 000 J
b. d = 200 m
c. F = 1200 N
d. F applied in forward direction = 1700 N.
14. v = 19 m/s

[wafisher]

3. 53,000 J
5. 37 cents
6. 45.0 degrees
9. 836 J/kg-C
19. 37500 J
21. 940,000 J

12. Answers can be yes or no, depending on sizes of bowls and masses of water. A larger bowl and mass of cold water can equal the thermal energy of a smaller bowl and mass of cold water. (How can this help you answer correctly the sense-nonsense question about the cup of hot water and the bathtub of cold water?

13. Potato has a large specific heat so it loses heat slowly.

14. Floor is not colder! It's at the same temperature! It just feels colder of higher conductivity.

28. 118,000 J
30. PE at top turns into thermal energy at the bottom.
32. 0.293 C
34. No! Disorder is always increasing. In physics talk, we say entropy increases.
36. ME = sum of KE and PE of the ball considered as one mass. Thermal Energy is the sum of the KE and PE of the individual particles of the ball. Temperature is a measure of the intenal energy of the ball.
38. No! Some go faster, some slower.
39. No! The metal doorknob is a better conductor of heat, so more heat flows from your hand and the metal door knob feels colder! But it's the same temperature!
41. Yes! When you melt a solid or boil a liquid. Going through a phase change, temperature remains constant!
45. No difference! Water is still 100 degrees C in both cases!
47. Al melts more ice! It's specific heat is higher than lead, so it has more heat capacity.
50. Cup A will be hotter because it contains more thermal energy.

52. 16,400 J
53. 1000 J/kg-K
57. 12.7 degrees
61. 6.68 x 10^6 J
63. 29 degrees C
65. 290 degrees
66. 10 meters
82. 10 times in one hour

77. answers will vary...

[wafisher]

1. T = .00472 seconds
2. v = 45 m/s
3. v = 9.03 m/s
4. wavelength = 0.55 m
5. look up superposition in your textbook and summarize in 2-3 sentances.
6. Diffraction occurs at each hole, produces two sets of circular waves that interfere with each other. This produces alternating lines of nodes and antinodes.
7. wavelength = 5.28 m
8. f = 58 Hz
9. d = 1200 m
10. wavelength = 0.986 m
11. t = 11.3 sec
12. f = 410 Hz
13. f = 330 Hz

[wafisher]

Practice Problems: odd number are in BOB!

2. 85 m
4. 140 m
6. 489 Hz

Section Reviews:

12. speed and wavelength affected, frequency and amplitude not affected
13. frequency and amplitude
15. velocity sound in greater in solids
17. No! doppler effect only occurs with relative motion.

Mastering Concepts:
32. light travels faster than sound
34. All Types!
37. resonance

Applying Concepts
42. Speed sound = distance / time
343 m/s = 1000 m / 3 seconds so sound travels about 1 km in 3 seconds. For miles it's 5 miles = 1 sec
43. a. no change in frequency b. wavelength increased
44. a. sound cannot travel in a vacuum! b. if it did, you would still not hear the sound the same instance you saw the flash

Mastering Problems
52. 1.7 km
53. 510 m
55. 98000 Hz
63a 349 m/s b. 0.436 s
69a 335 Hz b. 356 Hz

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1C 2D 3A 4C 5D 6A 7A 8B 9C 10C

11C 12D 13D 14C 15 D 16 B 17D 18B 19B 20B

21B 22B 23C 24A 25B 26C 27B 28C 29B 30A

31C 32C 33C 34B 35B 36A 37D 38A 39C 40A

41D 42B 43C 44B 45D 46B 47D 48A 49C 50D

51C 52D 53B 54A 55C 56D 57C 58A 59A 60A

[wafisher]

Here are answers to the 3Q EOC Assessment Review Questions...

CH 9 Momentum
1. p =mv 2. impulse 3. velocity 4. impulse
5. momentum (energy and/or mass also are good answers!) 6. six times! 7. 400 kg m/s 8. v = 15 m/s
9. v = 6 m/s

CH10 & 11 Work and Energy

10. 1/2 mv^2 11. 4x 12. W = change in E
13. joules 14. W = Fd 15. W = F cos (theta) d
16. W = mgh 17. P = W/t or mgh/t or F v
18. No! there is no change in energy!
19. No! same reason as #18
20. same - same!
21. mechanical
22. 4x
23. 43 meters

CH12 Heat and Temperature and Thermodynamics
24. KE 25. thermal energy 26. equal 27. heat, hot to cold 28. specific heat 29. Temperature
30. increase, more disorder 31. Q, W and U (U is the internal energy of the system) 32. 75 degrees C

Ch14 Waves
33. energy, matter 34. electromagnetic 35. 2 m/s
36. refraction 37. diffraction 38. 3.0 x 10^8 m/s for ALL e/m waves! 39. 250 m/s 40. minus 135 degrees Celcius. 41. medium; cycles per second

Ch15 Sound
42. 343 m/s 43. pitch 44. doppler 45. increases
46. 2100 meters 47. 1450 m/s 48. 5130 m/s
49. 4.76 seconds (two-part problem!)

[wafisher]

Ch 16

1. 1/9 3. graph 5. 8000 lm 6. 3.2 m 9. 27 cd

11. 9000 m 12. 3.840 E8 m 40. Eb = 1/2 Ea

53. 2.0 lux 55. need the 100W bulb! (1620 lm)

57. 1310 lm 65. 2.3 m 67. 15 m

STP 4. B 6. D 7. C 8. D

____________________________________________

CH 17 2. a. 42 b. 48 c. 84 3. 35 5. 60

6. 10 8. specular: window glass, smooth water, polished metal.

53. 38 54. a. 53 b. 106 56. 1.2 m behind the mirror, set lens to 2.4 meters for focus 74. 62

STP 5 C

___________________________________________
CH 18 2. 27.7 3. 22.1 5. 1.5 6. between 1.33 and 1.52 7. 1.46 53. A has larger index of refraction

67. a. 1.33 b. water 69.a. 25.4 b. 28.9

70. 1.24 E 8 m/s 71. 24.4 72. 49.7 99. 2.7 min

STP 1. c 2. d 8. D
_____________________________________________

[wafisher]

PLEASE PAY ATTENTION TO SIGNIFICANT FIGURES!
The general rule is: your answer should NOT have more significant figures than the least amount of significant figures in any of the numbers you used to calculate your answer!

1. f = 7.5 E 14 Hz color is violet
2. P = 2000 lm
3. f = 9.09 E 14 Hz
4. d = 3.8 E 16 m
5. E = 7.3 lx (note lux = lx)

6. d = 8.4 m
7. ultraviolet (see spectrum and read answer)
8. n = 1.40
9. v = 1.32 E8 m/s (note, it is less than 3.0 E8 m/s!)
10. n = 1.36

11. water has the larger index of refraction
12. difference = 2.0 E 6 m/s about 2 million times!
13. v = 2.26 E 8 m/s
14. 51 cm behind the mirror (or 102 cm from the object)
15. 32 degrees

[wafisher]

Unit XII A Static Electricity: Answers to Problem Set #1

Chpater 20:

9. 16,000 N an attractive force. (can also write - 16,000 N. A negative sign means an attractive force).
10. + 3.0 x 10E-6 C 10E-6 means micro coulombs!
12. 0.068 N to the right (This is Do (K)now # 1 (A-day).

20. Equal in magnitude, opposite in direction! Similar to the forces between the sun and earth! They are = and opposite. Can you say " Newton's third law!".
34. This is induction! The negative charge in the cloud, makes the Earth positive; the electric field that develops attracts negative charge to the earth.
36. both: inverse square law applies; product of masses or products of charges; different: gravitational force ALWAYS attractive; electrical force can be attractive or replusive.
39. need to decrease d such that d^2 = 1/3. or 0.58 times closer.
41. Gravitational forces ALWAYS attractive; Electrical forces can be + or - so vector sum for electrical forces are very small.
42a. 2F b. 1/4F c. 1/9F d. 4F e. 3/4 F
43. 1.6 x 10E20 electrons
44. 1.0 E-8 Newtons away from each other
46. 0.30 m
48. 98N east
49. 5.2 E-7 C, 1.5E-6 C
50. a. 5 x 10E22 atoms b. 1 x 10E24 electrons c. 2 x 10E5 C
52. 14N
54. 5 E-8 C
58. 1.6 E -8 C
64. varies

STP : 1D 2C 3A 4C 5A 6C 7D 8A 9B 10 0.46 N in the positive direction

[wafisher]

Chapter 21

1. 40 N/C
3. 8.1 E-6 N
5. a. No! b. Yes! Answers in BOB.
7. Electric field obeys the inverse square law, so new field is 1/4 of old field, or 6500 N/C.
8. 25,000 N/C away from the positive charge
10. 7.7 m
12. 6.25E4 N/C east
16. 300 V
17. 20,000 N/C
19. 2.94 E -2 m
21. 4.5 J
23. 2.9 E -15 J
26/27 gravitational force is down, air friction is up. When equal the drop falls at constant velocity. 27 - 3.2E-19C, 2 electrons

44/45. Direction is the direction of a positive charge in the field. The closer together electric field lines are, the stronger the force.
47. I'll look at your drawings.
54. Metal box shields parts from electric fields. Electric fields DO NOT exist inside hollow conductors.
66. 2.8 E-5 C
68. 6.7 E-7 C
71. 3.0 E-4 N
76. 50 V
77. 1.4 J
80. 90 V
90. 6.4 E-6 J
STP 1A 2D 3D 4C 5B

[wafisher]

Unit 12 Electricity Practice Test

1. (more challenging problem!) I1= 1.5A, I2=3.0A, V1=90V, V2=18V, V3= 12V

2a. draw 2b. 6.0 ohms 2c. I =1A 2d I = 0.75 A 2e V2= 2.3 V

3. total current of 15.5A is less than 20A so fuse will NOT melt!

4 R = 6.2 ohms
5a R = 6.5 ohms 5b. I = 6.5A 5c. I1 = 3.0A, I2 = 3.5 A d 42V
(Use tic-tac-toe to solve!)

6a R = 9.0 ohms 6b. I = 0.67A 6c. 0.67 A 6d. V1= 2.7V, V2=3.4V

7a. I =16.7A 7b. R = 7.19 ohms 7c. $3.36
8. 124 cents per year

9a. R = 10.4 A 9b. when the toaster is first turned on, its temperature is low and resistance is low, so the current is greater

10 R = 20.0 ohms
11a. I = 2.3 A 11b. E = 14,000 J

12. P = 25 W
13. P =145 W
14. 0.160 A
15a. P = 9.5W 15b. E = 1200 J