Physics deals with matter on scales ranging from subatomic particles (i.e. the particles that make up the atom and the particles that make up those particles).The dictionary definition of physics is “the study of matter, energy, and the interaction between them”
Absolute humidity:  The ratio of water vapor in a sample of air to the volume of the sample. 
Absolute zero:  The temperature of  273.16 or 0 K at which molecular motion vanishes. 
Absorptance:  The ratio of the total absorbed radiation to the total incident radiation. 
Acceleration:  The rate of change of velocity with respect to time. 
Acceleration due to gravity:  The acceleration imparted to bodies by the attractive force of the earth or any other heavenly body. 
Achromatic:  capable of transmitting light without decomposing it into its constituent colors. 
Acoustics:  The science of the production, transmission and effects of sound. 
Acoustic shielding:  A sound barrier that prevents the transmission of acoustic energy. 
Adiabatic:  Any change in which there is no gain or loss of heat. 
Afocal lens:  A lens of zero convergent power, whose focal points are infinitely distant. 
Albedo:  The fraction of the total light incident on a reflecting surface, especially a celestial body, which is reflected back in all directions. 
Alpha particle:  The nucleus of a helium atom (two protons and two neutrons) emitted as radiation from a decaying heavy nucleus. 
Alternating current:  The electric current that changes its direction periodically. 
Amorphous:  Solids which have neither definite form nor structure. 
Ampere:  S.I. Unit of electric current, one ampere is the flow of one coulomb of charge per second. 
Amplitude:  The maximum absolute value attained by the disturbance of a wave or by any quantity that varies periodically. 
Angle of contact:  The angle between tangents to the liquid surface and the solid surface inside the liquid, both the tangents drawn at the point of contact. 
Angle of incidence:  The angle between the incident ray and the normal. 
Angle of reflection:  The angle between the reflected ray and the normal. 
Angle of refraction:  The angle between the refracted ray and the normal. 
Angle of repose:  The angle of inclination of a plane with the horizontal such that a body placed on the plane is at the verge of sliding. 
Angstrom:  A unit of length, 1 = 1010 m. 
Angular momentum:  Also called moment of momentum, it is the cross product of position vector and momentum. 
Angular velocity:  The rate of change of angular displacement with time. 
Annihilation:  A process in which a particle and antiparticle combine and release their rest energies in other particles. 
Antineutrino:  The antiparticle of neutrino, it has zero mass and spin ½. 
Archimedes principle:  A body immersed in a fluid experiences an apparent loss in weight which is equal to the weight of the fluid displaced by the body. 
Atomic mass unit:  It is equal to onetwelfth the mass of C 12 isotope of carbon, 1 amu = 1.66x 1027 Kg. 
Atomic number:  The number of protons in an atomic nucleus. 
Avogadro number:  The number of molecules in a gram molecular weight of a substance, it is equal to 6.02 x 1023. 
Avogadro's law:  Under the same conditions of temperature and pressure, equal volumes of all gases contain equal number of molecules. 
Balmer lines:  Lines in the spectrum of hydrogen atom in visible range, produced by transition between n 2 and n = 2, n is the principal quantum no. 
Bar:  A unit of pressure, equal to 105 Pascals. 
Baryon:  subatomic particle composed of three quarks. 
Beat:  A phenomenon of the periodic variation in the intensity of sound due to superposition of waves differing slightly in frequency. 
Bernoulli's theorem:  The total energy per unit volume of a nonviscous, incompressible fluid in a streamline flow remains constant. 
Beta particle:  An electron emitted from a nucleus in radioactive decay. 
Binding energy:  The net energy required to decompose a system into its constituent particles. 
Black body:  An ideal body which would absorb all incident radiation and reflect none. 
Black hole:  The remaining core of a supernova that is so dense that even light cannot escape. 
Boyle's law:  For a given mass of a gas at constant temperature, the volume of the gas is inversely proportional to the pressure. 
Brewster's law:  States that the refractive index of a material is equal to the tangent of the polarizing angle for the material. 
Brownian motion:  The continuous random motion of solid microscopic particles when suspended in a fluid medium due to the consequence of ongoing bombardment by atoms and molecules. 
Bulk's modulus of elasticity:  The ratio of normal stress to the volumetric strain produced in a body. 
Buoyant force:  upward force on an object immersed in fluid. 
Calorie:  A unit of heat, 1Calorie = 4.186 joules. 
Candela:  The S.I. unit of luminous intensity defined as the luminous intensity in a given direction of a source that emits monochromatic photons of frequency 540 x 1012 Hz & has a radiant intensity in that direction of 1/683 W/sr 
Capacitance:  The ratio of charge stored per increase in potential difference. 
Capacitor:  Electrical device used to store charge and energy in the electrical field. 
Capillarity:  The rise or fall of a liquid in a tube of very fine bore. 
Carnot's theorem:  No engine operating between two temperatures can be more efficient than a reversible engine working between the same two temperatures. 
Centrifugal force:  An outward pseudo force acting on a body in circular motion. 
Centripetal force:  The radial force required to keep an object moving in a circular path; it is equal to mv2/r. 
Charles' law:  For a given mass of a gas at constant pressure, the volume is directly proportional to the temperature. 
Chromatic aberration:  An optical lens defect causing color fringes, because the lens brings different colors of light to focus at different points. 
Clausius' statement of second law of Thermodynamics:  It is not possible that at the end of a cycle of changes heat has been transferred from a colder body to a hotter body without producing some other effect. 
Closed system:  The system which cannot exchange heat or matter with the surroundings. 
Coefficient of linear expansion:  The increase in length per unit original length per degree rise in temperature. 
Coefficient of superficial expansion:  The increase in area per unit original area per degree rise in temperature. 
Coefficient of volumetric expansion:  The increase in volume per unit original volume per degree rise in temperature. 
Coherent source:  A source in which there is a constant phase difference between waves emitted from different parts of the source. 
Condensation point:  The temperature at which a gas or vapor changes back to liquid. 
Conduction:  The transfer of heat from a region of higher temperature to a region of lower temperature by increased kinetic energy moving from molecule to molecule. 
Convection:  The transfer of heat by the actual transfer of matter. 
Coulomb's law:  The force between any two charges is directly proportional to the product of charges and inversely proportional to the square of the distance between the charges. 
Critical angle:  The angle of incidence in a denser medium for which angle of refraction is . 
Cyclotron:  A device used to accelerate the charged particles. 
Decibel:  Unit of sound level, if P1 & P2 are two amounts of power, the first is said to be n decibels greater, where n = 10 log10 (P1/P2) 
Density:  The mass of a substance per unit volume. 
Diffraction:  The bending of light around the corners of an object. 
Dioptre:  Unit of power of a lens. 
Direct current:  An electrical current which always flows in one direction. 
Dispersion:  The splitting of white light into its component colors. 
Displacement:  The shortest distance between the initial and final position of a moving body. It is a vector quantity. 
Distance:  The actual path length covered by a body. It is a scalar quantity. 
Doppler Effect:  The apparent change in the frequency of a wave due to relative motion between the source and the observer. 
Einstein mass energy relation:  E = mc2, E is the energy released, m is the mass defect and c is the speed of light. 
Electric current:  The rate of flow of electric charge. 
Electric field line:  An imaginary curve tangent to which at a point gives the direction of electric field at that point. 
Electric potential energy:  The energy due to the position of a charge near other charges. 
Electrical conductors:  The materials that have free electrons and allow current to flow through them. 
Electrical insulators:  The materials which do not allow current to flow through them. 
Electrical resistance:  The property to oppose the flow of current. 
Electromagnetic induction:  The process in which current is induced in a coil whenever there is a change in the magnetic flux linked with the coil. 
Electron volt:  The energy gained by an electron when it passes through a potential difference of one volt, it is equal to 1.60 x 1019 Joules. 
Endothermic process:  The process in which heat is absorbed. 
Exothermic process:  The process in which heat is evolved. 
Escape Velocity:  The minimum velocity with which an object must be thrown upwards so as to overcome the gravitational pull, it is equal to , where M is the mass of the planet and R is the radius of the planet. 
Farad:  The S.I.unit of capacitance, defined as the capacitance of a capacitor that, if charged to 1 C, has a potential difference of 1 V. 
Faraday:  The electric charge required to liberate gram equivalent of a substance. 1 Faraday = 96485 coulomb/mole. 
Fermat's principle:  An electromagnetic wave takes a path that involves the least time when propagating between two points. 
Fluids:  Matter that has the ability to flow. 
Focus:  The point to which rays that are initially parallel to the axis of a lens or mirror are converged or from which they appear to diverge. 
Fraunhoffer lines:  The dark lines in the spectrum of sun. 
Free fall:  The motion of a body under the effect of gravity alone. 
Frequency:  The number of oscillations completed in 1 second by an oscillating body. 
Fundamental frequency:  The lowest frequency at which a system vibrates freely. 
Gamma ray:  A high energy photon. 
Graham's law of diffusion:  The rate of diffusion of a gas is inversely proportional to the square root of its density. 
Gravitational constant (G):  The constant of proportionality in Newton's law of gravitation, G = 6.67 x 1011 Nm2/kg2 
Gravitational potential at a point:  The amount of work done against the gravitational forces to move a particle of unit mass from infinity to that point. 
Gravitational potential energy:  The energy possessed by a body due to its position. 
Gravity:  The gravitational attraction at the surface of a planet or other celestial body. 
Ground state:  The lowest energy state of an atom. 
Halflife:  The time during which half the number of atoms in the element disintegrate. 
Heisenberg uncertainty principle:  It is impossible to have a particle that has an arbitrarily welldefined position and momentum at the same time. 
Hertz:  The unit of frequency, also known as cycles per second. 
Hooke's law:  Within elastic limit, stress is directly proportional to strain. 
Horsepower:  unit of power, 1H.P. = 746 Watts. 
Huygens'principle:  Each point on a light wavefront can be regarded as a source of secondary waves, the envelope of these secondary waves determining the position of the wavefront at a later time. 
Icepoint:  The melting point of ice under 1 atm pressure, it is equal to 0 or 32. 
Ideal gas Equation:  PV = nRT 
Impulse:  The product of force and time for which force acts, also equal to the change in momentum. 
Inertia:  The property of a body to resist a change in its state of rest or of uniform motion. 
Infrasonic:  Sound waves of frequency less than 20 Hz, below the range of human hearing. 
Insulators:  Materials like wood that are poor conductors of heat or electricity. 
Interference:  The redistribution of energy due to superposition of waves from coherent sources, resulting in alternate light and dark bands. 
Internal energy:  Sum of the kinetic energy and potential energy of all molecules of an object. 
Isobaric process:  In which pressure remains constant. 
Isochoric process:  In which volume remains constant. 
Isothermal process:  In which temperature remains constant. 
Isotope:  atoms of the same element with same atomic no (no of protons) but different mass no (no of neutrons). 
Joule:  The unit of work and energy, 1J = 1Nm. 
Joule's law of heating:  The heat produced when a current 'I' flows through a resistor 'R' for a given time't' is given by Q =I2Rt. 
Kelvin's statement of second law of thermodynamics:  It is impossible that, at the end of a cycle of changes, heat has been extracted from a reservoir and an equal amount of work has been produced without producing some other effect. 
Kinetic energy:  The energy possessed by a body due to its motion, it is equal to ½ mv2, where m is the mass and v is the speed of the body 
Kepler's first law of planetary motion:  Each planet moves in an elliptical orbit, with the sun located at one of the foci. 
Kepler's second law of planetary motion:  The radius vector joining the planet to the sun covers equal areas in equal intervals of time. 
Kepler's third law of planetary motion:  The square of the period of a planet is directly proportional to the cube of the radius of the semi major axis of the orbit. 
Kilocalorie:  The amount of energy required to raise the temperature of one kilogram of water by 1 , 1 Kcal = 1000 calories. 
Laser:  A device that produces coherent light by stimulated emission of radiation. 
Latent heat of fusion:  The quantity of heat required to convert one unit mass of a substance from solid to the liquid state at its melting point without any change in its temperature. 
Latent heat of sublimation:  The quantity of heat required to convert one unit mass of a substance from solid to gaseous state without any change in its temperature. 
Latent heat of vaporization:  The quantity of heat required to convert one unit mass of a substance from liquid to gaseous state at its boiling point without any change in its temperature. 
Law of Conservation of Energy:  Energy can neither be created nor destroyed, but can be transformed from one form to another. 
Law of conservation of mass:  Mass can neither be created nor destroyed in a chemical reaction. 
Law of conservation of momentum:  In the absence of external forces, the total momentum of a group of interacting objects remains constant. 
Lenz's law:  The induced current always flows in such a direction that it opposes the cause producing it. 
Lightyear:  The distance traveled by light through empty space in one year, it is equal to 9.46 x 1012 km. 
Longitudinal strain:  The ratio of change in length of a body to its initial length. 
Longitudinal wave:  The particles of the medium oscillate in the direction of propagation of the wave. 
Luminosity:  The total amount of energy radiated each second from the surface of a source. 
Lyman series:  A group of lines in the ultraviolet region in the spectrum of hydrogen. 
Magnetic domain:  Small regions in permanent magnets within which atomic or molecular magnetic moments are aligned parallel. 
Magnetic field:  The region around a magnet where its magnetic force is experienced by other magnetic objects. 
Magnetic reversal:  The changing of polarity of the earth's magnetic field as the north magnetic pole and the south magnetic pole exchange positions. 
Magnetic wave:  The spread of magnetization from a small portion of a substance where an abrupt change in the magnetic field has taken place. 
Magnification:  The ratio of the size of the image to the size of the object. 
Malus law:  The intensity of the light transmitted from the analyzer varies directly as the square of the cosine of the angle between the plane of transmission of analyzer and polarizer. 
Maser:  Microwave amplification by stimulated emission of radiation. 
Mass defect:  The difference between the sum of the masses of the individual nucleons forming a nucleus and the actual mass of that nucleus. 
Mass number:  The sum of the number of protons and neutrons in a nucleus. 
Mean life:  The average time during which a system, such as an atom, nucleus, exists in a specified form. 
Mechanical energy:  The sum of energy possessed by a body due to its position, configuration and motion. 
Mechanical wave:  The waves, which need a material medium for their propagation, e.g., Sound waves. 
MeV:  Unit of energy, equal to 1.6 x 1013 joules. 
Megahertz:  Unit of frequency, equal to 106 hertz. 
Millibar:  A measure of atmospheric pressure equivalent to 1000 dynes per cm 2. 
Modulus of elasticity:  The ratio of stress to the strain produced in a body. 
Modulus of rigidity:  The ratio of tangential stress to the shear strain produced in a body. 
Mole:  The amount of a substance that contains Avogadro's number of atoms, ions, molecules, or any other chemical unit; a mole is 6.02 x 1023 atoms, ions, or other chemical units. 
Momentum:  The product of mass and velocity of a body, it is a measure of the quantity of motion in a body. 
Monochromatic light:  Consisting of single wavelength. 
Natural frequency:  The frequency, with which a system oscillates in the absence of external forces, it depends on the size, composition, and shape of the object. 
Newton:  The unit of force, equal to the force that will produce an acceleration of 1m/s2 in a body of mass1 kg. 
Newton's first law of motion:  A body continues in a state of rest or of uniform motion in a straight line unless it is acted upon by an external (unbalanced) force. 
Newton's law of gravitation:  The gravitational force of attraction acting between any two particles is directly proportional to the product of their masses, and inversely proportional to the square of the distance between them. The force of attraction acts along the line joining the two particles. 
Newton's second law of motion:  The rate of change of momentum is directly proportional to the force applied. 
Newton's third law of motion:  To every action there is an equal and opposite reaction. 
Nuclear fission:  The splitting a heavy nucleus into more stable, lighter nuclei with an accompanying release of energy. 
Nuclear force:  The strong force that exists between the nucleons. 
Nuclear fusion:  The combination of two lighter nuclei to form a heavier nucleus with an accompanying release of energy. 
Nucleons:  A collective name for protons and neutrons. 
Nucleus:  The central, positively charged, dense portion of an atom. 
Ohm:  Unit of resistance; 1 ohm = 1volt/ampere. 
Ohm's law:  The current flowing through a conductor is directly proportional to the potential difference across the ends of the conductor. 
Open system:  A system across whose boundaries both matter and energy can pass. 
Optical fiber:  A long, thin thread of fused silica, used to transmit light, based on total internal reflection. 
Oscillatory motion:  The to and fro motion of a body about its mean position. 
Pascal:  A unit of pressure, equal to the pressure resulting from a force of 1 Newton acting uniformly over an area of 1m2. 
Pascal's law:  The pressure exerted on a liquid is transmitted equally in all directions. 
Paschen series:  A group of lines in the infrared region in the spectrum of hydrogen. 
Pauli Exclusion Principle:  No two electrons in an atom can have the same four quantum numbers; thus, a maximum of two electrons can occupy a given orbital. 
Peltier effect:  The evolution or absorption of heat at the junction of two dissimilar metals carrying current. 
Period of oscillation:  The time required for one complete oscillation. 
Periodic motion:  The motion which repeats itself after regular intervals of time. 
Photoelectric effect:  The emission of electrons in some materials when light of suitable frequency falls on them. 
Photons:  A quanta of energy in light wave; the particle associated with light. 
Planck's constant:  The ratio of energy to frequency, equal to 6.63 x 1034 joulesec. 
Plasma:  A highly ionized gas composed entirely of equal number of positive ions and electrons. 
Plasticity:  The property of a solid whereby it undergoes a permanent change in shape or size when subjected to a stress. 
Polarized Light:  Light whose constituent transverse waves are all vibrating in the same plane. 
Polaroid or polarizer:  A device that produces polarized light. 
Positron:  An elementary particle having same mass as that of an electron but equal and positive charge. 
Potential Energy:  The energy possessed by a body by virtue of its position or configuration. 
Power:  The rate of doing work. 
Pressure:  The force per unit area. 
Primary colors:  Three colors red, yellow and blue, which can be combined in various proportions to produce any other color. 
Principle quantum number:  A quantum number that describes the main energy level of an electron in terms of its most probable distance from the nucleus. 
Progressive wave:  A wave which transfers energy from one part of a medium to another. 
Projectile:  An object which after being given an initial velocity is allowed to fall under the effect of gravity alone. 
Quanta:  Fixed amounts; usually referring to fixed amounts of energy absorbed or emitted by matter. 
Quantum limit:  The shortest wavelength, present in a continuous xray spectrum. 
Quantum mechanics:  Model of the atom based on the wave nature of subatomic particles, the mechanics of electron waves; also called wave mechanics. 
Quantum numbers:  Numbers that describe energy states of an electron. 
Quark:  One of the hypothetical basic particles, having charges whose magnitudes are onethird or twothird of the charge on an electron. 
Q unit:  A unit of energy, used in measuring the heat energy of fuel reserves, equal to 1018 British thermal units, or approximately 1.055x1021 joules. 
Radiant energy:  The form of energy that can travel through space; for example, visible light and other parts of the electromagnetic spectrum. 
Radiation:  The emission and propagation of waves transmitting energy through space or through some medium. 
Radioactive decay:  The natural spontaneous disintegration or decomposition of a nucleus. 
Radioactive decay constant:  A specific constant for a particular isotope which is the ratio of the rate of nuclear disintegration per unit time to the total number of radioactive nuclei. 
Radioactive decay series:  Series of decay reactions that begin with one radioactive nucleus that decays to a second nucleus that decays to a third nucleus and so on until a stable nucleus is reached. 
Radioactive decay law:  The rate of disintegration of a radioactive substance is directly proportional to the number of undecayed nuclei. 
Rarefaction:  A part of a longitudinal wave in which the density of the particles of the medium is less than the normal density. 
Real image:  An image which can be projected on a screen. 
Rectilinear Motion:  The motion of a body in a straight line. 
Reflection:  The bouncing back of a wave from a boundary. 
Refraction:  The bending of light from its straight line path when it travels from one medium to another. 
Refractive index:  The ratio of speed of light in vacuum to that in the medium. 
Relative density:  The ratio of density of a substance to the density of water at 4 . 
Relative humidity:  The percentage of the amount of water vapor actually present in a certain volume of the air to the amount of water vapor needed to saturate it. 
Resolving power:  A quantitative measure of the ability of an optical instrument to produce separable images of different points of an object. 
Resonance:  When the frequency of an external force matches the natural frequency of the body then the body oscillates with large amplitude. 
Restoring force:  The force which tends to bring an oscillating body towards its mean position whenever it is displaced from the mean position. 
Resultant Force:  A single force, which acts on a body to produce the same effect in it as, done by all other forces collectively. 
Reverberation:  The prolongation of sound at a given point after direct reception from the source has ceased, it is due to reflections from the boundary surfaces. 
Rigid body:  An idealized extended body whose size and shape is fixed and remains unaltered when forces are applied. 
Saturated air:  Air in which equilibrium exists between evaporation and condensation; the relative humidity is 100 percent. 
Scalar Quantity:  A physical quantity, which is described completely by its magnitude. 
Second's Pendulum:  A simple pendulum whose time period on the surface of earth is 2 seconds. 
Semiconductors:  Elements whose electrical conductivity is intermediate between that of a conductor and an insulator. 
Shear strain:  The ratio of the relative displacements of one plane to its distance from the fixed plane. 
Shear stress:  The restoring force developed per unit area when deforming force acts tangentially to the surface of body producing change in the shape of the body without any change in volume. 
Siemens:  The derived S.I. unit of electrical conductance, equal to the conductance of an element that has a resistance of 1 ohm, also written as ohm1. 
Simple harmonic motion:  The vibratory motion that occurs when the restoring force is proportional to the displacement from mean position and is directed opposite to the displacement. 
Snell's law:  The ratio of sin i to sin r is a constant and is equal to the refractive index of the second medium with respect to the first. 
Solenoid:  A cylindrical coil of wire that becomes electromagnetic when a current flows through it 
Sonic boom:  Sound waves that pile up into a shock wave when a source is traveling at or faster than the speed of sound. 
Specific heat:  The amount of heat energy required to increase the temperature of one gram of a substance by 1 . 
Speed:  The distance traveled by a body per unit of time. 
Spin quantum number:  From quantum mechanics model of the atom, one of four descriptions of the energy state of an electron wave; this quantum number describes the spin orientation of an electron relative to an external magnetic field. 
Standing waves:  The waves formed due to superposition of two waves of same frequency and traveling in opposite directions with same speed. 
Steampoint:  It is the temperature of steam over pure boiling water under 1 atm pressure. It is equal to 100 or 212 . 
StefanBoltzmann law:  The amount of energy radiated per second per unit area of a perfectly black body is directly proportional to the fourth power of the absolute temperature of the surface of the body. 
Superconductors:  Some materials in which, under certain conditions, the electrical resistance approaches zero. 
Surface tension:  The property of a liquid due to which its surface behaves like a stretched membrane. 
Tesla:  The S.I. unit of magnetic flux density, defined as the magnetic flux density of a magnetic flux of 1 Wb through an area of 1m2. 
Thermal Capacity:  The quantity of heat required to raise the temperature of the whole body by 1 . 
Thermal Equilibrium:  When the two bodies in contact are at the same temperature and there is no flow of heat between them, these are said to be in thermal equilibrium. 
Thermal Expansion:  The increase in the size of an object on heating. 
Total internal reflection:  Condition where all light is reflected back from a boundary between materials; occurs when light travels from denser to rarer medium and angle of incidence is greater than the critical angle. 
Transverse wave:  A wave in which the particles of the medium oscillate in a direction perpendicular of the direction of propagation of wave. 
Trough:  The point of maximum negative displacement on a transverse wave. 
Ultrasonic Sound:  Sound waves of frequencies above 20,000Hz. 
Uniform Circular Motion:  The motion of an object in a circular path with uniform speed. 
Unpolarized light:  Light consisting of transverse waves vibrating in all possible random directions. 
Van der Wall's force:  General term for weak attractive intermolecular forces 
Vector Quantity:  A quantity, which needs both magnitude and direction to describe it. 
Velocity:  Distance traveled by a body in a particular direction per unit time or the displacement of the body per unit time. It is a vector quantity. 
Vibration:  A back and forth motion that repeats itself. 
Virtual image:  An image formed when the reflected or refracted light rays appear to meet; this image cannot be projected on a screen. 
Volt:  Unit of potential difference, equivalent to joule/coulomb. 
Voltage drop:  The electric potential difference across a resistor or other part of a circuit that consumes power. 
Watt:  S.I. unit for power; equivalent to joule/sec. 
Wavelength:  The distance between the two nearest points on a wave, which are in the same phase or the distance between two adjacent crests or two adjacent troughs. 
Wave motion:  The movement of a disturbance from one part of a medium to another involving the transfer of energy but not the transfer of matter. 
Wave period:  The time required for two successive crests or other successive parts of the wave to pass a given point. 
Wave velocity:  The distance traveled by a wave in one second. 
Weight:  The force with which a body is attracted towards the center of the earth. The weight of a body of mass m is given by mg, where g is the acceleration due to gravity. 
Weightlessness:  The state when the apparent weight of a body becomes zero. 
Wien's displacement law:  For a black body, the product of the wavelength corresponding to maximum radiance and its absolute temperature is constant. 
Work:  Work is done when force acting on a body displaces it. Work = Force x Displacement in the direction of the force. 
Zeeman Effect:  The splitting of the spectral lines in a spectrum when the source is exposed to a magnetic field.  
Zeroth law of thermodynamics:  If
body A is in thermal equilibrium with body B, and B is also in thermal
equilibrium with C, then A is necessarily in thermal equilibrium with C.All Physics Formula and Glossary
Glossary
