1. Distance is the total length that an object in motion covers. Displacement is a
vector quantity that indicates the change in position that an object moves in a
particular direction. Average speed is the distance covered per unit time. Average
velocity is the displacement divided by the time interval.
2. Acceleration occurs whenever there is a change of speed or direction of motion.
3. Free fall problems can be solved like other acceleration problems by substituting
'a' for 'g' = .The sign of 'g' is (+) or (-) depending on the choice of up
or down as the positive direction. It is OK to use 'g' = in the multiple
choice section of the exam.
4. A ball rolled off a horizontal table will take the same amount of time to hit the ground as another dropped from the same height.
5. Projectile motion:
a. horizontal and vertical components are independent,
b. the horizontal component of the velocity remains constant, the vertical
component has constant acceleration 'g',
c. only the vertical component of the velocity at the maximum height is zero,
d. for projectiles fired at an angle you may assign negative signs to all vectors
going down.
Work, Energy and Momentum
12. Work and energy are scalar quantities.
13. Work is equal to the product of the displacement and the component of the
force in the direction of the displacement.
14. For an object traveling in circular motion, the centripetal force never does work.
15. Mechanical energy is the sum of all kinetic and potential energies.
16. Work-Energy Theorem: the net work is equal to the change in kinetic energy.
17. Conservation of mechanical energy under the action of a dissipative force
includes the work due to frictional forces (non-conservative forces).
18. Power is the time rate of change of work or energy, but it can also be calculated
using force x speed.
19. The impulse is the product of the average force and the time interval through
which it acts. Impulse is equal to the change in momentum.
20. Momentum is conserved in all collision systems. Kinetic energy is conserved
only in elastic collisions.
21. Objects stick together in perfectly inelastic collisions.
Waves and Sound
77. Transverse wave particles vibrate perpendicular to the wave direction
and longitudinal wave particles vibrate parallel to the direction of the wave
propagation.
78. Sound waves are mechanical longitudinal waves. Light waves are
electromagnetic transverse waves.
79. The speed of a wave depends only on the properties of the medium.
80. The energy of a wave is directly proportional to the square of the amplitude.
81. The intensity of sound is inversely proportional to the distance.
82. Superposition Principle: When two or more waves exist simultaneously in the
same medium, the resultant amplitude at any point is the algebraic sum of the
amplitudes of each wave.
83. The harmonics produced in open pipes are similar to those produced in strings.
The fundamental occurs when the length of the pipe (or string) equals 1/2 λ.
84. The fundamental on a closed pipe occurs when the length of the pipe equals
1/4 λ. Only the odd harmonics are possible for a closed pipe.
85. Whenever two waves exist simultaneously in the same medium and they are
nearly at the same frequency, beats are set up.
86. Doppler effect is the apparent change in frequency of a source of sound when
there is relative motion of the source and the listener.
Geometric and Physical Optics
87. The wave behavior of light is proven by diffraction, interference and the
polarization of light.
88. The particle behavior of light is proven by the photoelectric effect.
89. The electromagnetic spectrum (radio, microwaves, infrared, visible, ultraviolet,
x-ray and gamma rays) is listed from lowest frequency to highest (longer to
smaller wavelength).
90. The range of wavelengths for visible light goes from 400 nm for violet to
700 nm for red.
91. All angles in reflection and refraction are measured with respect to the normal.
92. At the critical angle a wave will be refracted to 90 degrees.
93. Total internal reflection occurs at angles greater than the critical angle.
94. Light rays bend away from the normal as they enter a lower index of refraction
medium while the frequency remains constant.
95. Light bends toward the normal and has a shorter wavelength when it enters a
higher index of refraction medium while the frequency remains constant.
96. In Young's double-slit experiment interference and diffraction account for the
production of bright and dark fringes.
97. Single slit diffraction produces a much wider central maximum than double slit.
98. Waves in phase undergo constructive interference; waves out of phase (1/2 λ)
will undergo destructive interference.
99. When light reflects from a medium with higher index of refraction than that of
the medium in which it is traveling, a 180˚ phase change (1/2 λ) occurs.
100. For a single optical device, real images are always inverted and virtual images
are always upright.
101. Concave mirrors are converging and convex mirrors are diverging.
Concave lenses are diverging and convex lenses are converging.
102. Convex mirrors and concave lenses produce only small virtual images.
Magnetism
68. Magnetic fields point from the north to the south outside the magnet.
69. A particle entering a magnetic field between two plates will follow a circular path.
The magnetic force provides the centripetal force.
70. Magnetic force on a charged particle is at its maximum when the field and
velocity vectors are at right angles. The force is at a minimum (0) when the field
and velocity vectors are parallel or antiparallel.
71. Right hand rules are for positive charges, for negative charges the direction is
the opposite of the one found with the right hand rule.
72. Moving electric charges (current) creates magnetic field (Oersted), but a
changing magnetic field creates an electric current (Faraday).
73. Relative motion between a conductor and a magnetic field induces an emf in
the conductor.
74. The direction of the induced emf depends upon the direction of motion of the
conductor with respect to the field.
75. The magnitude of the emf is directly proportional to the rate at which the
conductor cuts magnetic flux lines.
76. According to Lenz's law, the induced current must be in a direction that
opposes the change that produced it.
Atomic and Nuclear Physics
103. The kinetic energy of the ejected electrons is the energy of the incident
radiation minus the work function of the surface.
104. Increasing light frequency increases the kinetic energy of the emitted
photoelectrons.
105. Increasing light intensity increases the number of emitted photoelectrons
but not their kinetic energy.
106. Below a certain frequency, called the threshold frequency no electrons are
emitted no matter how intense the light beam.
107. Stopping potential is the value of the difference in potential between two
plates that is just sufficient to stop the most energetic photoelectrons emitted.
108. De Broglie proposed that all objects have wavelengths related to their
momentum.
109. The lowest energy state of an atom is called the ground state.
110. Emission spectra are photons leaving the atom as electrons come down
energy levels. Absorption spectra are photons being absorbed as electrons
move up energy levels from the ground state.
111. Alpha particles are the same as helium nuclei: 2 protons, 2 neutrons. Beta particles are electrons, and gamma “particles” are photons.
112. The mass of a nucleus is always less than the sum of the masses of the
nucleons. This mass defect is converted into binding energy. (E=mc^2).
One amu of mass is equal to 931 MeV of energy.
113. Nuclear fusion is a reaction in which two nuclei are combined to form a large
nucleus. Fusion is the source of energy in stars.
114. Nuclear fission is a reaction in which a nucleus is split.
Circular Motion and Gravitation
22. Uniform circular motion refers to motion in a circle where the speed is constant
and only the direction changes. The change in direction produced by a central
force is called centripetal acceleration.
23. The centripetal force is not a special kind of force; therefore never label a force
on a free-body-diagram as 'centripetal'. The centripetal force is provided by the
component of the force that is directed towards the center of the circular path.
24. The gravitational force is directly proportional to the product of the masses
and inversely proportional to the square of the distance between them.
Thermal Energy and Thermodynamics
38. Thermal energy represents the total internal energy of an object, the sum of its
molecular kinetic and potential energies.
39. Kinetic theory relates the average kinetic energy of the molecules in a gas to the
temperature of the gas in Kelvins.
40. First Law of Thermodynamics: ΔU = W + Q
Where W is the work done ON the system.
41. Thermodynamic Processes:
- Adiabatic process: Q = 0
- Isovolumetric (isochoric) process: W = 0
- Isothermal process: ΔU = 0
- Isobaric process: ΔU = W + Q
42. On a PV diagram, if the cycle is clockwise the system is a heat engine and the
net work is negative.
If the cycle is counterclockwise the system is a refrigerator and the net work
is positive.
43. Carnot cycles involve only isothermal and adiabatic processes. To determine the
efficiency use the Kelvin temperatures of the reservoirs.
44. Second Law of Thermodynamics:
- Heat flows naturally from an object at higher temperature to one of lower
temperature.
- All natural systems tend toward a state of higher disorder (entropy).
Electricity
45. Coulomb's Law: the force of attraction or repulsion between two point charges
is directly proportional to the product of the two charges and inversely
proportional to the square of the separation between the charges.
46. Use the sign of the charges to determine the direction of the forces and
Coulomb's Law to determine their magnitudes.
47. Electric forces and electric fields are vectors, electric potentials are scalars.
48. Electric fields point in the direction of the force on a positive test charge.
49. The electric field inside a closed conductor is zero. Outside the conductor the
electric field is not zero and the electric field lines are drawn perpendicular to the
surface.
50. Electric field lines are perpendicular to equipotential lines.
51. Electric fields between two parallel plates are uniform in strength except at
the edges.
52. The electric potential energy increases as a positive charge is moved against
the electric field, and it decreases as a negative charge is moved against the
same field.
53. The energy gained by a charged particle that is accelerated through a potential
difference can be expressed in electronvolts (eV):
54. The electric potential (V) is equal to the work per unit charge.
55. No work is done in moving a charged object along an equipotential line.
56. Capacitance is the ratio of charge to the potential for a given conductor.
57. The capacitance for a parallel-plate capacitor depends on the surface area of
each plate, the plate separation and the permittivity or dielectric constant.
58. A source of electromotive force (emf) is a device that converts chemical,
mechanical, or other forms of energy into electric energy.
59. Resistance depends on the kind of material (resistivity), the length, cross
sectional area, and temperature. Resistance is proportional to length and
inversely proportional to cross-sectional area.
60. All resistors in parallel have equal voltage. Adding a resistor in parallel
decreases the total resistance of a circuit.
61. All resistors in series have equal current. Adding a resistor in series increases
the total resistance of a circuit.
62. Voltmeters have a high resistance (to keep from drawing current) and are wired
in parallel (because voltage is the same in parallel). Ammeters have a low
resistance (to keep from reducing the current) and are wired in series (because
current is the same in series).
63. Kirchhoff's First Rule: The sum of all the currents entering a junction point
equals the sum of all the currents leaving the junction point. This rule is based
on the conservation of electric charge.
64. Kirchhoff's Second Rule: The algebraic sum of all the gains and losses of
potential around any closed path must equal zero. This rule is based on the
law of conservation of energy.
65. All capacitors in parallel have equal voltage. The total charge is equal to the
sum of the charges and the effective capacitance is the sum of the individual
capacitances.
66. All capacitors in series have equal charge. The potential difference across the
battery is equal to the sum of the drops across each capacitor.
67. For circuits that contain capacitors and resistors:
- A capacitor that is empty allows the flow of current such as a wire.
- A capacitor that is full acts like a broken wire.
UNITS
MEASUREMENT
MEASUREMENT
UNIT
SYMBOL
EXPRESSED IN
BASE UNITS
EXPRESSED IN
OTHER SI UNITS
Acceleration
m/s2
m/s2
Capacitance
Farad
F
A2.s4/kg.m2
Current
Ampere
A
C/s
Electric charge
Coulomb
C
A.s
Electric field
N/C
kg.m/C.s2
Electric resistance
Ohm
W
kg.m2/A2.s3
V/A
Energy, work
Joule
J
kg.m2/s2
N.m
Emf, voltage
Volt
V
kg.m2/A.s3
Force
Newton
N
kg.m/s2
Frequency
Hertz
Hz
s-1
Magnetic field
Tesla
T
kg/A.s2
N.s/C.m or Wb/m2
Magnetic flux
Weber
Wb
kg.m2/A.s2
V.s
Pressure
Pascal
Pa
kg/ms2
N/m2
Potential
difference
Volt
V
kg.m2/A.s3
W/A or J/C
Power
Watt
W
Kg.m2/s3
J/s
Fluid Mechanics
31. Absolute pressure is equal to the gauge pressure plus the atmospheric
pressure.
32. Fluid pressure is independent of the shape or area of the container.
33. Archimedes' Principle: An object that is completely or partly submerged in a
fluid experiences an upward force (buoyant force) equal to the weight of the
fluid displaced.
34. An object will float (sink) in a fluid if the density of the object is less (greater) than
the density of the fluid.
35. The submerged fraction of an object is the ratio of the submerged volume to the
total volume or the ratio of the density of the object to the density of the fluid.
36. Pascal's Principle: An external pressure applied to a confined fluid is transmitted
throughout the fluid.
37. Bernoulli's Equation: The net work done on a fluid is equal to the changes in
kinetic and potential energy of the fluid in terms of quantities per volume.
Forces
6. For free-body-diagrams draw only the forces acting on the object in question.
7. Newton's First Law: for objects at rest or moving at constant velocity the net
force is zero.
8. For Newton's Second Law: a net unbalanced force produces acceleration.
9. The normal force and the gravitational force are not an action-reaction pair.
10. Static friction exists between two surfaces when motion is impending; kinetic
friction occurs when two surfaces are in relative motion. In either case, the friction
forces are proportional to the normal force.
11. For inclined planes, the minimum coefficient of static friction
The Physics Concepts listed below are important Physics facts that students need
to know for semester and/or final examinations.
This list is NOT the only thing a student needs to know for an AP Physics exam! Being able to apply these concepts and physics equations using critical thinking
is more important than just rote memorization. Use these concepts for review purposes only!
For a printable pdf version of this list click here:
a. horizontal and vertical components are independent,
