Circular Motion, Center of Gravity and Universal Gravitation
Study Guide
1. Which horse has a greater linear speed, the horse near the outside rail or the
horse near the inside rail of a merry-go-round? (Hint: Think of class demo!)
-The outside horse
2. Same scenario as above, but which horse has a greater angular speed?
-They both have the same speed.
3. The difference between a rotation and a revolution is what? What do they spin
around?
Rotation: External Axis, Revolution: Internal Axis
4. What type of force is in action on a washing machine? What happens to the
clothes when the washing cycle is complete?
-Outward force, clothes move to the outside.
5. A string is tied on to a can. You begin to spin the can round and round above your
head. Whats the deal with the forces acting on the can?
-There is an inward force acting on the can.
6. Centrifugal forces are what kind?
-Center fleeing
7. Why do people weigh less at the equator? What is the reason for this?
-The spin of the Earth
8.If a car is traveling in a circle at a constant speed, what would the net force on the
car be?
-The force is directed toward the center of the course.
9. True of False. A straight line about which rotation takes place is called an axis.
-True
10. True of False. Any force that causes an object to move in a circular path is called
a centripetal force.
-True
11. Where is the center of gravity for a softball bat. A car. A doughnut. A cup of
coffee.
-Bat: Barrel
Doughnut: the hole
-Car: Towards the center, bottom Coffee: Center of the cup.
12. Where is the center of gravity typically located?
-The center of mass above the base of support.
13. Why do you think we keep asking you about the object that’s center of gravity is
located where there is no mass?
-Because there is are a few questions that revolve around COG!
14. What is the correlation between center of gravity and base of support?
-Not over its base of support.
15. When you carry a heavy load in one hand what do you typically do with the
other hand? Why?
-To change the center of gravity and the load.
16. What happened to you when you tried to bend over and touch your toes with
your back and feet against the wall? Why?
-Your center of gravity is outside your support area.
17. What do monkeys use their tails for?
-Allows the monkey to control and change its center of gravity.
18. Does the center of gravity for a person change? If yes, give an example.
-As a person bends over, it can change.
19. Linear speed is:
-The distance moved over a unit of time.
20. Tangential speed is:
-The speed of something moving along a circular path.
21. A tree is REALLY big. What do you think the roots look like?
-Very deep and broad.
22. Rotational speed is:
-The number of rotations per unit of time.
23. What did Newton think about the force on the moon and the force on an apple?
-Force on the moon is the same force on an apple.
24. What did Newton think about the tangential velocity of the moon?
-Is attracted to Earth & has tangential velocity that prevents it from falling.
25. What did Newton think about the gravitational attraction between Earth and the
moon?
-Gets smaller the farther away you get.
For 26 – 30, look through your PowerPoint!
26. When a train follows a curve, the __________outside___________ wheels travel
_________faster_____________ than the inside wheels?
27. The greater the masses, _____________________. The greater the force.
28. The greater the distance, _____________________. The smaller the force.
29. Know the difference between revolution and rotation!
-Internal v. external axis.
30. Hi. Hello.
31. What is the audible range of hearing for an average person?
-20-20,000 Hz
32. Where does sound travel fastest through? Solid, liquid or gas?
-Solid
33. What types of waves are sound waves?
-Sound waves are transverse waves.
34. What can’t sound waves travel through? (Hint: think space)
-Vacuum
35. What is the threshold of hearing?
-Minimum intensity an average human can hear
36. What needs to be the same for one tuning fork to make another tuning fork
vibrate without direct contact?
-The same frequency.
37. If a sound is getting louder, what is increasing?
-Intensity
38. What is pitch?
-The perceived frequency of a sound.
39. What is the unit for measuring intensity?
-W/m^2
40. Describe what happens when an ambulance (with its lights on and sirens on)
drives past you.
-The sound waves speed up as they get closer to you.
41. What can make the intensity of a sound change? (increasing or decreasing what?
[don’t say volume])
-The power of the source changes, or the distance changes.
42. Which is faster: the speed of sound or the speed of light?
-Slower
43. What are the 6 types of simple machines?
-Lever, pulley, axle, wheel, inclined plane, screw.
44. D = V*T and V = wavelength * frequency
45. What causes the music or sounds inside a music box?
-Vibrations and the sounding board.
46. What is resonance?
-An object is forced to vibrate at its natural frequency.
47. What frequencies can usually be heard by a normal person’s hearing?
-Audible
48. All sound is produced by what?
-Vibrating objects.
49. What can be measured by the energy of a vibrating object?
-Loudness
50. What is the formula for Velocity?
-V=t*d
51. How do you measure wavelength?
W =V/T
52. Unit of measurement for frequency is…
-Hz
53. Unit of measurement for intensity is…
-dB
54. Think to the video of the glass shattering with the opera singer. What was going
on there that made the glass shatter?
-Resonance
55. What is the Doppler effect?
-Using sound waves to determine distance.
56.
57. A harmonic wave is traveling along a rope. The source generating the waves
completes 50 to and fro motions in 25 s. A trough travels 2m in 4s. calculate the
wavelength of the wave? 8/2 = 4m
58.
59. What are two variables that can effect intensity of an object?
-Distance and power
60. What are the decibel levels that humans can hear? When does it become painful
for the ears? 0 dB
61. What frequencies can the human hear? Do younger and older people hear
different frequencies?
-1000 Hz
62. What makes an acoustic guitar ring out?
-Vibrations
63. What happens to the pitch of a car horn as a car passes you?
-It decreases
64. What happens to the size of a wavelength as the source of the vibrations starts to
move faster?
-Shorter
65. What is constructive interference? And what is destructive interference?
-Constructive: waves come together, destructive: waves cancel out.
66. How do we measure amplitude? Like, with a ruler. From where to where?
-Midline to crest.
67. How do we measure wavelength? Like, with a ruler. From where to where?
-Crest to crest/ trough to trough
68. What is frequency?
-Number of times the wave happens during a period.
69. What type of wave is sound?
-Longitudinal
70. Hertz. What is it?
-Unit of frequency.
71. What is a period in reference to waves?
-The number of times a wave vibrates each second.
72. Amplitude.
-Vertical distance from the midpoint to crest or trough.
73. Which type of wave has the shortest wavelength on the EMS?
-Gamma
74. What can influence the speed of a wave?
-Source, distance.
75. What types of waves are ocean waves?
-Surface waves.
76. What type of waves are electromagnetic waves? Transverse or longitudinal?
-Longitudinal
77. Can electromagnetic waves travel through a vacuum?
-Yes!
78. What is the shortest wave on the EM spectrum?
-x-Rays
79. Which has a bigger wavelength-UV rays or infrared rays?
-Longer
80. Which is faster-visible light or radio waves?
-Faster
81. What are some differences of radio waves and sound waves?
-Their basic nature.
82. How long does it take for sunlight to reach the earth?
-8 minutes.
83. What are the waves on the EM spectrum?
-Radio, Microwave, Infrared, Visible, UV, X-Ray, Gamma
84. What type of rays do heat lamps give off?
-Infrared
85. Compared to air, the speed of light in water is slower/faster/the same
-Slower
86. Can UV rays pass through glass?
-No
87. Do clouds transmit or block UV rays?
-Transmit
88. What color travels fastest through clear glass?
-Red
89. What does a shadow look like on a piece of paper?
-Sharp
90. What type of waves are light waves?
-Transverse
91. What determines the color of an object as we see it?
-Frequencies of light reflected back.
92. What color dominates sunlight?
-Yellow
93. What blocks most of the UV rays from hitting us on earth?
-Absorbed by the ozone layer.
94. On the moon, what color does the daytime sky look like?
-Grey.
95. What does the color on TV result from-addition or subtraction?
-Addition
96. What does the color on photographs result from-addition or subtraction?
-Subtraction
97. Why are tennis balls yellowy-green?
-That’s what the eye can most easily pick up.
98. Different colors of light correspond to different- intensities, frequencies,
velocities, velocities, or polarities?
-Frequencies.
99. What are complimentary colors?
-Produce white light.
100. What colors do we use for subtraction?
-Magenta, cyan and yellow.
101. What colors make up magenta?
-Red and blue.
102. Why is the sky blue?
-Particles reflect blue light.
103. Why are sunsets red?
-More particles throughout the atmospshere.
104. Why are clouds white?
-Scatter difference colors of light.
105. What color is water?
-Greenish blue.
106. What do you use to figure out what a star is made of?
-Spectroscope
107. What are the 3 primary colors?
Red, green, blue.
108. What color does mixing red and blue make?
-Magenta
109. The complimentary color of blue is?
-Magenta
110. Does glass transmit visible light?
-Yes
111. What is a light year?
-The distance light travels in one year.
112. What types of waves cause sunburn?
-Infrared.
113. What colors form black
-Absence of all colors.
114. What is the approximate speed of light?
-300, 000 km/s
115. What has the biggest wavelength on the EM spectrum?
-Microwaves