Physics Misconceptions

Sources of Wisdom

1. Positively charged objects have gained protons, rather than being deficient in electrons.
2. Electrons which are lost by an object are really lost (no conservation of charge).
3. All atoms are charged.
4. A charged object can only attract other charged objects.
5. The electrostatic force between two charged objects is independent of the distance between them.
6. Gravitational forces are stronger than electrostatic forces.
7. Batteries have electricity inside them.
8. Energy is a thing. This is a fuzzy notion, probably because of the way we talk about newton-meters or joules. It is difficult to imagine an amount of an abstraction.
9. The terms “energy” and “force” are interchangeable.
10. An object at rest has no energy.
11. The only type of potential energy is gravitational.
12. Gravitational potential energy depends only on the height of an object.
13. Doubling the speed of a moving object doubles the kinetic energy.
14. Energy can be changed completely from one form to another without energy loss.
15. Things “use up” energy.
16. Energy is confined to some particular origin, such as what we get from food or what the electric company sells.
17. Energy is truly lost in many energy transformations.
18. There is no relationship between matter and energy.
19. If energy is conserved, why are we running out of it?
20. The only “natural” motion is for an object to be at rest.
21. If an object is at rest, no forces are acting on the object.
22. A rigid solid cannot be compressed or stretched.
23. Only animate objects can exert a force. Thus, if an object is at rest on a table, no forces are acting upon it.
24. Force is a property of an object. An object has force and when it runs out of force it stops moving.
25. The motion of an object is always in the direction of the net force applied to the object.
26. Large objects exert a greater force than small objects.
27. A force is needed to keep an object moving with a constant speed.
28. Friction always hinders motion. Thus, you always want to eliminate friction.
29. Frictional forces are due to irregularities in surfaces moving past each other.
30. Rocket propulsion is due to exhaust gases pushing on something behind the rocket.
31. Time is defined in terms of its measurement.
32. The location of an object can be described by stating its distance from a given point (ignoring direction).
33. The terms distance and displacement are synonymous and may be used interchangeably. Thus the distance an object travels and its displacement are always the same.
34. Velocity is another word for speed. An object’s speed and velocity are always the same.
35. Acceleration is confused with speed.
36. Acceleration always means that an object is speeding up.
37. Acceleration is always in a straight line.
38. Acceleration always occurs in the same direction as an object is moving.
39. If an object has a speed of zero, even instantaneously, it has no acceleration.
40. Light is associated only with either a source or its effects. Light is not considered to exist independently in space; and hence, light is not conceived of as “traveling.”
41. An object is “seen” because light shines o it. Light is a necessary condition for seeing an object and the eye.
42. Lines drawn outward from a light bulb represent the “glow” surrounding the bulb.
43. A shadow is something that exists on its own. Light pushes the shadow away from the object to the wall or the ground and is thought of as a “dark” reflection of the object.
44. Light is not necessarily conserved. It may disappear or be intensified.
45. Light from a bulb only extends outward a certain distance, and then stops. How far it extends depends on the brightness of the bulb.
46. The effects of light are instantaneous. Light does not travel with a finite speed.
47. A mirror reverses everything.
48. For an observer to see the mirror image of an object, either the object must be directly in front of the mirror, or if not directly in front, then the object must be along the observer’s line of sight to the mirror. The position of the observer is no t important in determining whether the mirror image can be seen.
49. An observer can see more of his image by moving further back from the mirror.
50. The mirror image of an object is located on the surface of the mirror. The image is often thought of as a picture on a flat surface.
51. The way a mirror works is as follows: The image first goes from the object to the mirror surface.
52. Then the observer either sees the image on the mirror surface of the image reflects off the mirror and goes into the observer’s eye.
53. Light reflects from a shiny surface in an arbitrary manner.
54. Light is reflected from smooth mirror surfaces but not from non-shiny surfaces.
55. Curved mirrors make everything distorted.
56. Light shines on a translucent material and illuminates it so it can be seen. Light does not travel from the translucent material to the eye.
57. Light always passes straight through a transparent material without changing direction.
58. When an object is viewed through a transparent solid or liquid material the object is seen exactly where it is located.
59. Students will often think about how a lens forms an image of a self-luminous object in the following way. They envision that a “potential image” which carries information about the object leaves the self-luminous object and travels through the space to the lens. When passing through the lens, the “potential image” is turned upside down and may be changed in size.
60. When sketching a diagram to show how a lens forms an image of an object, only those light rays are drawn which leave the object in straight parallel lines.
61. Blocking part of the lens surface would block the corresponding part of the image.
62. The purpose of the screen is to capture the image so that it can be seen. The screen is necessary for the image to be formed. Without a screen there is no image.
63. An image can be seen on the screen regardless of where the screen is placed relative to the lens. To see a larger image on the screen, the screen should be moved further back.

64. An image is always formed at the focal point of the lens.
65. The size of the image depends on the diameter of the lens.
66. When a wave moves through a medium, particles of the medium move along with the wave.
67. Gamma rays, x-rays, ultraviolet light, visible light, infrared light, microwaves and radio waves are different entities.
68. When two pulses, traveling in opposite directions along a spring or rope meet, they bounce off each other and go back in the opposite direction.
69. Colors appearing in soap films are the same colors that appear in a rainbow.
70. Polaroid sunglasses are just dark glass or dark plastic.
71. All metals are attracted to a magnet.
72. All silver colored items are attracted to a magnet.
73. All magnets are made of iron.
74. Larger magnets are stronger than smaller magnets.
75. The magnetic and geographic poles of the earth are located at the same place.
76. The magnetic pole of the Earth in the northern hemisphere is a north pole, and the pole in the southern hemisphere is a south pole.
77. From the non-scientific point of view, “work” is synonymous with “labor.” It is hard to convince someone that more work is probably being done playing basketball for 30 minutes than studying for a test.
78. Failing to be able to identify the direction in which a force is acting.
79. Believing that any force times any distance is work.
80. Believing that machines put out more work than we put in.
81. Not realizing that machines simply change the form of work we doCtrade off force for distance or distance for force.
82. Loudness and pitch of sounds are confused with each other.
83. You can see and hear a distant event at the same moment.
84. The more mass in a pendulum bob, the faster it swings.
85. Hitting an object harder changes its pitch.
86. In a telephone, actual sounds are carried through the wire rather than electrical pulses.
87. Human voice sounds are produced by a large number of vocal chords.
88. Sound moves faster in air than in solids because air is “thinner” and forms less of a barrier.
89. Sound moves between particles of matter (in empty space) rather than matter.
90. In wind instruments, the instrument itself vibrates not the internal air column.
91. As waves move, matter moves along with them.
92. The pitch of whistles or sirens on moving vehicles is changed by the driver as the vehicle passes.
93. The pitch of a tuning fork will change as it “slows down,” or “runs” out of energy.
94. The pupil of the eye is a black object or spot on the surface of the eye.
95. The eye receives upright images.
96. The lens is the only part of the eye responsible for focusing light.
97. The lens forms and image (picture) on the retina. The brain then “looks” at this image and that is how we see.
98. The eye is the only organ for sight; the brain is only for thinking.
99. A white light source, such as an incandescent or fluorescent bulb, produces light made up of only one color.
100. Sunlight is different from other sources of light because it contains no color.
101. When white light passes through a prism, color is added to the light.
102. The rules for mixing color paints and crayons are the same as the rules for mixing colored lights.
103. The primary colors for mixing colored lights are red, blue and yellow.
104. A colored light striking an object produces a shadow behind it that is the same color as the light.
105. For example, when red light strikes an object, a red shadow is formed.
106. The shades of gray in a black and white newspaper picture are produced by using inks with different shades of gray.
107. When white light passes through a colored filter, the filter adds color to the light.
108. The different colors appearing in colored pictures printed in magazines and newspapers are produced by using different inks with all the corresponding colors.
109. The mixing of colored paints and pigments follow the same rules as the mixing of colored lights.
110. The primary colors used by artists (red, yellow and blue) are the same as the primary colors for all color mixing.
111. Color is a property of an object, and is independent of both the illuminating light and the receiver (eye).
112. White light is colorless and clear, enabling you to see the “true” color of an object.
113. When a colored light illuminates a colored object, the color of the light mixes with the color of the object.
114. Explanations of visual phenomena involving color perception usually involve only the properties of the object being observed, and do not include the properties of the eye-brain system.