SAT Subject Test Physics (2012)
GLOSSARY
absolute zero the lowest possible temperature at which all molecular motion would cease; 0 K
acceleration a change in velocity divided by the time required for the change to occur
alpha decay the spontaneous emission of an alpha particle, which is a helium nucleus, by certain radioactive substances
ammeter a device used to measure current
amplitude the maximum displacement of the particles of a medium
angular acceleration the rate of change in angular velocity over time
angular displacement a vector measure of the rotation of an object about an axis
angular momentum the product of the mass, velocity, and radius of motion
angular velocity the rate of change of angular displacement with respect to time
Archimedes’ Principle the rule stating that an object immersed in a fluid will experience a buoyant force equal to the weight of the fluid it displaces
atomic number the number of protons in the nucleus of an atom
average speed the total distance an object travels divided by the time during which it traveled that distance
average velocity the total change in displacement divided by the time during which the displacement occurred
balanced forces a combination of forces on an object that result in a net force of zero
beat the interference caused by two sets of sound waves with only slightly different frequencies
Bernoulli’s Principle the rule stating that as the speed of a moving fluid increases, the pressure exerted within the fluid decreases
beta decay the spontaneous emission of an electron or a positron by certain radioactive substances
binding energy the energy required to break apart an atomic nucleus; the difference in energy between the nucleons when they are separate and when they are bound together
Boyles’ Law the law that states that volume is inversely related to pressure if temperature is held constant
buoyant force the upward force exerted by a fluid on an object placed in it
capacitor an electrical device used to store charge
center of mass the point at which all the mass of an object can be considered to be located
centripetal acceleration the rate of change in velocity of a mass moving uniformly in a circle at constant speed; directed radially inward toward the center of the circular path
centripetal force the force directed inward along the radius of an object’s circular path
Charles’ Law the law that states that volume is directly proportional to temperature if pressure is held constant
circuit a closed path of conducting materials through which electricity can flow
coefficient of friction the ratio of the friction force between two surfaces and the normal force between those surfaces
concave lens a converging lens; a transparent piece of glass or plastic that is thicker in the middle than at the ends.
concave mirror a converging mirror; a reflective surface that curves away from an object
conduction the transfer of heat between materials that are in contact with one another
constructive interference the phenomenon that occurs when two waves combine in such a way that the amplitude of the resulting wave is greater than either of the two individual waves
convection the transfer of heat by the movement of a heated substance, such as by currents in a fluid
convex lens a diverging lens; a transparent piece of glass or plastic that is thicker at the ends than in the middle
convex mirror a diverging mirror; a reflective surface that bulges toward the object
Coulomb’s Law the law that states that the magnitude of the force between charged particles is proportional to the product of the two charges and varies inversely as the square of the distance between them
critical angle the angle of incidence at which the angle of refraction is 90° relative to the normal
cross product the combining of vectors in such a way that the result is a vector
current the amount of charge moving through a conductor per second
density the mass of a substance divided by its volume
destructive interference the phenomenon that occurs when two waves combine in such a way that the amplitude of the resulting wave is less than either of the two individual waves
diffraction the bending of waves around an obstacle or through an opening
direct relationship a correlation in which two variables increase or decrease simultaneously
displacement a change in position of an object, which is a vector quantity
distance the length between two points, which is a scalar quantity
domain a large groups of atoms with net spins that align
Doppler effect a relative change in frequency due to motion of a sound of source or its observer
dot product the combining of vectors in such a way that the result is a scalar
elastic potential energy the stored potential energy resulting when an object is deformed or distorted, such as a compressed spring
electric field intensity the magnitude of the electric field
electric field the force exerted on a charged particle by a charged object in the region around the object
electric potential the amount of work per unit charge required to move a charge from infinity to another point in an electric field
electromagnet a solenoid with an iron core, which forms a magnet that can be controlled
electromagnetic induction the process through which an electric current can be induced by a changing magnetic field
electromagnetic spectrum the arrangement of electromagnetic waves in order of wavelength
electromagnetic wave a traveling disturbance produced by vibrating charges; travels as a series of vibrating electric and magnetic fields at right angles to one another
electromagnetism the relationship between electricity and magnetism
electroscope an instrument used to determine the presence of small electric charges
energy the ability to do work or cause change to a system
entropy a measure of the disorder of a system
force a push or a pull
free-body diagram a picture used to compare the direction and magnitude of the forces exerted on an object
frequency the number of revolutions or waves per unit time
friction the resistive force that opposes the motion of an object as a result of the contact between two surfaces
gamma decay the spontaneous emission of high-energy photons by certain radioactive substances
generator a device that transforms mechanical energy into electrical energy
gravitational constant the constant G, which has a value of 6.67 × 10–11 N · m2/kg2, and is used in the equation to calculate the gravitational force
gravitational force the force of attraction between any pair of objects as a result of their masses
gravitational potential energy the energy an object has because of its position in a gravitational field
half-life the time it takes for half of the radioactive nuclei in a sample to decay
heat energy the transfer of thermal energy from a warmer substance to a cooler substance
heat engine a device that converts heat to mechanical energy by doing work
heat of fusion the amount of energy required to change a unit mass of a substance from a solid to a liquid at the melting point
heat of vaporization the amount of energy required to change a unit mass of a substance from a liquid to a gas at the boiling point
impulse the product of the average force exerted on a mass and the time interval over which the force is exerted; vector quantity
index of refraction: the ratio of the speed of light in a vacuum with the speed of light in a specific medium
indirect relationship a correlation in which the dependent variable changes opposite to the independent variable
instantaneous velocity the velocity of an object at a particular instant
internal energy the total amount of energy of the particles and includes potential energy in addition to kinetic energy
isotopes atoms of the same element with different numbers of neutrons
joule the unit of energy equal to one newton-meter
Joule’s Law of Heating the law that states that the heat produced is directly proportional to the square of the current, the resistance, and the time
kinetic energy the energy an object has as a result of its motion
kinetic friction the resistive force that opposes the movement of an object already in motion
kinetic theory the description of matter as being made up of small particles that are in constant motion
law of charges the law that states that unlike charges attract one another and like charges repel one another
law of conservation of energy the law that states that the total energy of a system remains constant; no new energy is created and no energy is destroyed
length contraction the phenomenon in which an observer at rest relative to a moving object traveling at relativistic speeds would observe the length of the object to be shorter than it would be at rest relative to the observer
longitudinal wave a wave in which the particles of the medium vibrate parallel to the direction of motion of the wave
mass defect the difference between the mass of the unbound nucleons and the mass of the bound nucleons
mechanical energy the total of the potential and kinetic energy of a system
mechanical wave a traveling disturbance that requires a medium through which to travel
momentum the product of the mass and velocity of a moving object; vector quantity
motor a device that transforms electrical energy into mechanical energy
natural frequency the frequency at which a system that has been disturbed will vibrate once there are no disturbing forces
normal force the reaction force exerted on an object by a surface in contact with the object
nuclear decay the process through which unstable nuclei release particles or energy in order to gain stability
nuclear fission a nuclear reaction in which one large nucleus splits to form smaller nuclei
nuclear fusion a nuclear reaction in which two smaller nuclei combine to form a larger one
Ohm’s Law the law that states that resistance is directly proportional to voltage and indirectly proportional to current.
parallel circuit a circuit through which current can follow multiple paths
Pascal’s Principle the rule stating that any external pressure applied to a confined static fluid is distributed uniformly throughout the fluid
photoelectric effect the phenomenon in which electrons along the surface of a metal are emitted when electromagnetic energy with a certain minimum frequency is incident on the metal
photon a discrete bundle, or quantum, of electromagnetic energy
pitch the characteristic of sound that describes how high or low it is perceived; determined by the frequency of the sound wave
potential energy the energy an object has as a result of its position or condition
power the rate at which work is done or energy is used
pressure the force per unit area
radiation the transfer of heat by electromagnetic waves, or particles given off by radioactive substances
radioactivity the spontaneous emission of radiation
real image an image formed by a mirror or lens that exists where rays meet, and which therefore can be focused on a screen
reflection the process through which light bounces off a surface
refraction the bending of a light ray when it passes at an angle from one medium to another
resistance the opposition to the flow of charges offered by a material
resonance: the tendency of a system to vibrate at a greater amplitude at some frequencies than others
resonant frequency a natural vibrating frequency of an object
right-hand rule a method of finding the direction of a magnetic field around a current-carrying wire or the force acting on a wire or charge in magnetic field
scalar quantity a quantity that is described by magnitude without regard to direction; examples include mass and temperature
scientific notation a shorthand notation for writing very large or small numbers using a coefficient that is greater or equal to 1 and less than 10 multiplied by base 10 to an exponent
series circuit a circuit through which current can flow through each element without branching
significant figures digits in a number that are known with some degree of certainty
Snell’s Law of Refraction the law that states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the relative index of refraction for the two mediums
solenoid a series of closely spaced coils of wire
special theory of relativity the theory proposed by Einstein that suggests that the speed of light is constant in all reference frames, despite any relative motion between an observer and the light source, and the laws of physics are the same in all inertial reference frames
specific heat the amount of heat required to raise the temperature of one mass unit by one degree Celsius
standing wave a stationary wave pattern formed when two sets of waves with equal wavelength and amplitude interfere
static friction the resistive force that opposes the start of motion between two surfaces in contact
strong force a short-range force that holds the nucleons of an atom together despite the like charges of the protons
temperature the average kinetic energy of the molecules in a sample of matter
thermal energy the total kinetic energy of all the particles in a sample of matter
threshold frequency the minimum frequency of the incident electromagnetic energy on a metal for the photoelectric effect to be observed
time dilation the phenomenon in which an observer at rest relative to a moving object traveling at relativistic speeds would observe the length of time to be longer than it would be at rest relative to the observer
torque the tendency of a force to cause rotation about an axis, which is measured as the product of the force and the length of the lever arm
total internal reflection the process in which light incident on the boundary between two mediums, passing from the medium with the higher index of refraction, is reflected back into the original medium
transverse wave a wave in which the particles of the medium vibrate perpendicular to the direction of motion of the wave
unbalanced forces a combination of forces on an object that do not result in a net force of zero
uniform circular motion motion around a circle at a constant speed
uniformly accelerated motion motion in which an object accelerates at a constant rate
vector quantity a quantity that is described by both magnitude and direction; examples include force and acceleration
virtual image an image formed by a mirror or lens that exists where rays appear to meet, but do not, and therefore cannot be focused on a screen
voltage potential difference, or the amount of electric potential
voltmeter a device used to measure voltage
wave a disturbance that carries energy from one location to another
wavelength the distance between similar points on consecutive waves
weight the product of mass and the acceleration due to gravity at a particular location
work the product of the force exerted on an object and the distance the object moves as a result of that force
work-energy theorem the idea that the work done on a system or by a system equals the change in the energy of the system