Physics Flashcards
Positron
an anti-electron, denoted beta+ or e+, emitted in a nuclear reaction
Radiation
Form of heat transfer accomplished by electromagnetic waves, which can travel through a vacuum
Capacitor
an electric device used in circuits that is composed of two conducting plates separated by a short distance. When voltage is applied to it, a capacitor stores electric charge
bulk modulus
a term that describes a substance’s resistance to compression under a pressure, denoted by the variable B and measured by the ratio of stress (pressure change) to strain: changeP/(changeV/V)
Fundamental Unit of Charge
the smallest measured electric charge,which belongs to a single proton or electron; this charge is equal to 1.6 X 10^-19 C, and is positive for a proton and negative for an electron
Acceleration
A vector quantity describing a change in velocity over the elapsed time during which that change occurs, expressed as a=changeV/changeT
Velocity
a vector quantity describing an object’s displacement over the elapsed time, expressed as v=changeX/changeT
Potential Difference
the difference in electric potential between two points in an electric field, also termed the voltage (changeV)
Force
a vector quantity describing a push or pull on an object. The SI unit for force is the Newton (N)
Weight
a force that measures the gravitational pull on an object, given by the object’s mass times its gravitational acceleration (mg, where g is 9.8m/s^2 on Earth)
Half-Life
the amount of time it takes for one-half of a radioactive sample to decay, given by the equation t 1/2 = (ln2)/lambda, where lambda is a decay constant
Gamma Decay
the atom emission of high energy photons, also known as y-particles
electric dipole
the effect, often found in chemical bonds, of having two charges of opposite sign and equal magnitude separated by a short distance d
torque
the magnitude of a force acting on a body times the perpendicular distance between the acting force and the axis of rotation, denoted by the Greek letter T with the SI units N*m
Resonance
if a standing wave undergoes a forced oscillation due to an external periodic fore that has a frequency equal to the natural frequency of the oscillating system, resonance will occur, and the amplitude of the standing wave will approach its maximum
Converging Lens
A lens with a thick center that converges light rays at a point where the image is formed
Diverging Lens
a lens with a thin center that diverges light after refraction and always forms a virtual image
Exponential Decay
a decrease in the amount of substance N through radioactive decay, given by the equation: N=N0 X e^-lambdaT
Ferromagnetic
a material whose atoms have net magnetic field and, below a critical temperature, are strongly attracted to a magnet pole
Power
the rate at which work is done, given by the equation P=W/changeT, where W is work and T is time in seconds
Kinetic Energy
the energy of an object resulting from the objects motion through space, calculated by the equation KE =1/2mv^2 and given in the SI unit of Joules (J)
Magnetic Force
a force exerted on a charged particle moving through a magnetic field, calculated using the equation FB = qvBsin0. The sin0 represents the fact that only the component of motion perpendicular to the magnetic field contributes to the magnetic force on the particle
Work Function
The minimum amount of photon energy required to emit an electron form a certain metal. This quantity, denoted by the letter W, is used to calculate the residual kinetic energy of an electron emitted by a metal, given by KE =hf - W, where hf is the energy of a photon
Amplitude
in a wave, the point of maximum displacement from equilibrium
electric field
the electrostatic force that a source charge qs would exert on a positive test charge q0 within its proximity divided by the magnitude of that test charge; E = Fcoul/q0
Calorie
a unit for heat. A calorie (lowercase c) is equal to 4.184 J, but an alternate unit, the Calorie (uppercase C, also abbreviated kcal) equals 1,000 calories, or 4,184 Joules
Work-Energy Theorem
a theorem stating that the net work performed on an object is related to the change in kinetic energy of that body, given by the equation W = changeKE
Hooke’s Law
the equation describing the restoring force of a mass-spring system, given by F= -kx, where x is the dispalcement from the equilibrium position
Converging Mirror
A concave mirror with a positive focal length that converges light rays at a point where the image is formed
Speed
a scalar quantity describing the distance traveled over the time required to travel that distance
Thermal Expansion
the expansion of a solid as a result of increasing temperatures, calculated by the equation changeL = aLchangeT, where L is length, a is the coefficient of linear expansion of the material, and T is the temperature
Fluorescence
the phenomenon observed when an atom is excited by UV light and the electrons return to the ground state in two or more steps, emitting photons of lower frequency (often in the visible light spectrum) at each step.
Density
a scalar quantity defined as the mass per unit volume, often denoted by the Greek letter p
Electromotive Force
The energy gained by an electron when it is accelerated through a potential difference of 1 volt, given by qV where q is 1.6 x 10^-19 C and V is 1 volt
Current
the flow of charge as it moves across a potential difference (voltage), denoted by the letter I and measured by the amount of charge passing through a conductor over a unit of time: changeQ/changeT
Magnetic Field
field vectors created by moving charges and permanent magnets that in turn exert a magnetic force on moving charges and current-carrying wires
Diverging Mirror
a convex mirror with a negative focal length. Diverging mirrors always produce virtual images.
Center of Mass
The point on an object or body, calculated by averaging the distribution of mass in each dimension, at which all of the objects mass can be considered to be concentrated
Doppler Effect
when a source emitting a sound and a detector receiving the sound move relative to each other, the virtual frequency f’ detected is less than or greater than the actual frequency source and detector move toward or away from each other f’ = f (v +- vD)/v+-vS)
Law of reflection
law stating that when light waves strike a medium, the angle of incidence 0i is equal to the angle of reflection 0r
Viscosity
the measure of internal friction in a liquid, often denoted by the Greek letter n
Vector
a quantity that has both magnitude and direction
Absolute Pressure
the pressure below the surface of a liquid, depending on gravity and surface pressure and calculated by p= P0 + pgz, where P0 is the surface pressure, p is the density of the fluid, g is the acceleration due to gravity, and z is depth (the vertical distance from the surface)
Conservation of Momentum
the momentum of a system remains constant when there are no net external forces acting on it
Volume Expansion
the expansion in volume of a liquid as a result of increasing temperatures, calculated by the equation changeV = betaVchangeT, where V is volume and beta is the coefficient of volume expansion of the material, and T is the temperature
Rotational Equilibrium
State where the sum of the torques acting on a body is zero, giving it no net angular acceleration
Photoelectric Effect
The phenomenon observed when light above a certain frequency is incident on a sheet of metal and causes it to emit an electron
Direct Current
Current that flows through a conductor in one direction only
Dielectric
an insulating material placed between the two plates of a capacitor. When a dielectric is inserted, if the circuit is plugged into a current source, more charge will be stored in the capacitor; if the circuit is not plugged into a current source, the voltage of the capacitor will decrease
Work
the quantity measured when a constant force acts on a body to move it a distance d, calculated by the equation W = Fdcos0. The cos0 represents the fact that only the component of the force parallel to the direction of motion is considered
