Homework Helpers: Physics

GLOSSARY

A

Absolute Zero: Theoretically, the lowest temperature that an object can reach. At this temperature, the kinetic energy of a molecule will be zero.

Acceleration: The rate at which an object’s velocity changes.

Adiabatic Process: A process in which no heat is gained or lost by the system.

Alpha Decay: The process of radioactive decay involving the release of an alpha particle from the nucleus of an atom.

Alpha Particle: A particle consisting of two protons and two neutrons, with the identical composition of the nucleus of a helium atom.

Alternating Current (AC): Electric current that periodically reverses directions.

Amplitude: The maximum displacement of the particles of a medium from their rest position.

Angle of Incidence: The angle formed between the incident, or incoming, ray and the line drawn perpendicular (normal) to the boundary of the medium.

Angle of Reflection: The angle formed between the reflected, or outgoing, ray and the line drawn perpendicular (normal) to the boundary of the medium.

Angular Displacement: The change of position of a rotating body as measured by the angle through which it rotates.

Angular Velocity: The rate at which a body rotates in a particular direction. The rate of change of an object’s angular displacement.

Aphelion: The point in its orbit where a planet is furthest from the sun.

Atomic Number: The number of protons in the nucleus of an atom.

Average Velocity: The total displacement of an object divided by the time elapsed during this period of time.

B

Beta Decay: The process of radioactive decay involving the release of a beta particle (an electron) from the nucleus of an atom, resulting in a neutron transforming into a proton.

Beta Particle: A particle (an electron) emitted from the nucleus of an atom during beta decay.

Beta-Plus Decay: The process of radioactive decay involving the release of a positron from the nucleus of an atom, resulting in a proton transforming into a neutron.

Boyle’s Law: The pressure and volume of an ideal gas at constant temperature are inversely proportional to each other.

C

Capacitance: The ability of a capacitor to store electrical charge as its potential rises.

Capacitor: A device that stores an electric charge.

Center of Curvature: The center of the sphere of which the mirror or lens forms a part.

Centripetal Acceleration: Acceleration directed toward the center of a circular path.

Centripetal Force: A force directed toward the center of a circular path, which is responsible for keeping an object moving in circular motion.

Charles’s Law: The volume of an ideal gas at constant pressure varies directly with its kelvin temperature.

Circular Motion: The motion of a body along a circular path.

Coefficient of Friction: The ratio of the force of static or kinetic friction to the normal force.

Component Vector: One of a set of two or more vectors that can be added to form a resultant vector.

Compression: An area in a material medium where the particles are more densely packed.

Concave Lens: A diverging lens.

Concave Mirror: A curved mirror with the shiny surface on the inside of the curve.

Convex Lens: A converging lens.

Convex Mirror: A curved mirror with the shiny surface on the outside of the curve.

Conduction (as the term relates to electrostatics): The process of charging an object by bringing it into direct contact with another charged object.

Constant Acceleration: A state in which the acceleration is constant. If the acceleration is nonzero, the velocity changes at a constant rate.

Constant Velocity: A state in which neither the speed nor the direction of the object changes.

Constructive Interference: The addition of two or more waves resulting in a greater net disturbance than each of the individual waves.

Contact Force: A force between two objects that are in direct contact with each other.

Conventional Current: Visualization of current flowing out of the positive terminal into the negative terminal.

Coulomb’s Law: The electrostatic force between two charged objects is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

Crest: The highest point on a wave.

Critical Angle of Incidence: The minimum angle of incidence to produce total internal reflection.

D

Destructive Interference: The addition of two or more waves resulting in a smaller net disturbance than the individual waves.

Deuterium: An isotope of hydrogen with one proton and one neutron.

Diffraction: The spreading out of a wave beyond a barrier.

Diffuse Reflection: A reflection in which the reflected rays are not parallel to each other.

Direct Current (DC): Electric current that flows in one direction.

Displacement (as the term relates to motion): A vector quantity that describes the change in an object’s position in terms of direction and distance.

Doppler Effect: The apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves.

E

Elastic Collision: A collision in which the total kinetic energy is conserved.

Elastic Potential Energy: The energy stored in an object that has been compressed or stretched.

Electric Circuit: An arrangement of components that provides one or more pathways for electric current to flow.

Electric Current: The rate at which electrically charged particles flow through a material.

Electric Field: An area of space around a charged object in which another charged object will experience a force.

Electric Field Lines: Lines drawn to represent the magnitude and direction of the force exerted by the electric field on a positive test charge, per unit of its charge.

Electric Field Strength: How much force a charged object within the field experiences at that position, per units of its charge.

Electric Potential Energy: The energy that a charged object has due to its location in an electric field.

Electric Potential: The electric potential energy of a charged object, divided by its charge.

Electric Power: The rate at which electrical energy is transformed.

Electromagnetic Induction: The production of a voltage in a conducting circuit by moving it through an external magnetic field, or by changing the magnetic field.

Electromagnetic Wave: A transverse wave that is capable of traveling through a vacuum.

Electron: A negatively charge particle commonly found in the “cloud” area surrounding the nucleus of an atom.

Electron Cloud: The area surrounding the nucleus of an atom, where the electron(s) can be found.

Electron Volt: The energy required to move an electron between two points that have a difference of potential of one volt. 1 eV = 1.6 × 10-19 J

Electroscope: A device that is used to detect electrostatic charge.

Energy: The capacity for doing work.

F

Field Force: A force that acts on objects without touching them.

Focal Length: The distance measured from the vertex of a mirror or lens to its focal point.

Focal Point: The point to which light converges, from which light diverges.

Force: Something that causes a change in an object’s velocity.

Free Fall: The condition of an object that is falling with uniform acceleration caused by gravity.

Frequency: The number of vibrations or cycles of motion in a second, usually measured in Hertz.

Friction: A force that exists between two objects that are touching, which resists their motion relative to each other.

G

Gamma Decay: The radioactive decay of an atom accompanied by the release of high-energy photons.

Gravitational Potential Energy: The energy that an object possesses due to its position in a gravitational field.

Grounding: Providing a conductive path between a charged object or a circuit to the ground.

H

Hadron: A particle made up of quarks.

Hooke’s Law: Below the elastic limit, strain is proportional to stress.

Horizontal Projectile Motion: Projectile motion in which all of the initial velocity is along the horizontal (x) axis.

I

Impulse: The product of a force and the time interval during which the force acts.

Induction: The process of charging an object by bringing it near a charged object and providing a pathway for charge between the neutral object and the ground.

Inelastic Collision: A collision in which the kinetic energy is not conserved.

Inertia: An object’s tendency to resist changes in motion.

Instantaneous Acceleration: The change in velocity at a particular instant.

Instantaneous Velocity: The velocity of an object at a particular instant.

Interference: The overlapping of two or more wave disturbances.

Ion: An atom that has gained or lost one or more electrons.

Isobaric Process: A process in which the pressure of the gas remains the same.

Isometric Process: A process in which the volume of the gas remains the same.

Isothermal Process: A process in which the temperature of the gas remains the same.

Isotopes: Two or more forms of atoms of the same elements, containing the same number of protons but different numbers of neutrons.

K

Kepler’s First Law of Planetary Motion: The orbits of the planets are ellipses, with the sun at 1 focus of the ellipse.

Kepler’s Second Law of Planetary Motion: The line joining the planet to the sun sweeps out equal areas in equal times as the planet travels around the ellipse.

Kepler’s Third Law of Planetary Motion: The ratio of the squares of the revolutionary periods for two planets is equal to the ratio of the cubes of their semimajor axes.

Kinematics: The study of the motion of objects without regard to the causes of motion.

Kinetic Energy: The energy that an object possesses due to its motion.

Kinetic Friction: The force of friction between two objects that are in motion relative to each other.

L

Law of Reflection: The angle of incidence is equal to the angle of reflection.

Lepton: An elementary particle with very small or insignificant mass.

Linear Momentum: The product of the mass and velocity of an object.

Longitudinal Wave: A wave in which the particles of the medium vibrate back and forth along the same axis in which the wave travels.

M

Magnetic Declination: The angle between geographic north and magnetic north.

Magnetic Domain: A microscopic region in which the magnetic fields of atoms are aligned in the same direction.

Magnetic Field: The region of space around a magnetized object in which a magnetic force can be detected.

Magnetic Field Line: Lines representing the magnitude and direction of the magnetic field.

Magnetic Field Strength: The intensity of a magnetic field.

Mass Defect: The difference between the mass of the individual nucleons that make up a nucleus and the nucleus itself.

Mass Number: The total number of protons and neutrons in the nucleus of an atom.

Mechanical Energy: The sum of the kinetic and all forms of potential energy.

Mechanical Wave: A wave that requires a medium through which to travel.

Mechanics: The branch of physics that deals with the motion of objects.

Momentum: The product of the mass and velocity of an object.

N

Negative Ion: An atom that has gained one or more electrons.

Net Force: The vector sum of all of the forces acting on an object.

Newtonian Mechanics: The branch of physics dealing with the motion of macroscopic objects.

Newton’s First Law of Motion: In the absence of an unbalanced force, an object in motion will remain in motion, and an object at rest will remain at rest.

Newton’s Law of Universal Gravitation: Two bodies attract each other with a force that is directly proportional to the product of their masses, and inversely proportional to the square of the distance between them.

Newton’s Second Law of Motion: The acceleration an object experiences is directly proportional to the net force exerted upon it and inversely proportional to its mass.

Newton’s Third Law of Motion: When an object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.

Normal Force: A force exerted by one object on another object in a direction that is perpendicular to the surface of contact.

Nuclear Fission: The process in which a heavy nucleus splits into two or more parts.

Nuclear Fusion: The process in which two or more smaller nuclei combine to make a larger one.

Nucleon: A particle (a proton or neutron) found in the nucleus of an atom.

P

Parallel Circuit: A circuit with more than one path for current to flow.

Perihelion: The point in its orbit where a planet is closest to the sun.

Period: The amount of time required to complete one vibration or cycle of motion.

Photons: Tiny packets of energy.

Polarization: The process of inducing a temporary separation of charges in a neutral object by bringing it in close proximity to a charged object.

Positive Ion: An atom that has lost one or more electrons.

Positron: The antiparticle of the electron.

Potential Difference: The difference in electric potential between two points.

Power: The rate of doing work, measured in watts.

Pressure: The amount of force exerted per unit of area.

Primary Axis: A line drawn from the vertex of a mirror or lens, through the focal point and center of curvature.

Projectile Motion: The motion of an object that experiences free fall, after being given some amount of horizontal velocity.

Protium: An isotope of hydrogen with one proton and no neutrons in its nucleus.

Proton: A positively charged particle commonly found in the nucleus of an atom.

Pulse: A short, non-repeated disturbance.

Q

Quantum Mechanics: The branch of physics that deals with very small scales.

Quark: Fundamental particles that are constituents of protons and neutrons.

R

Radian: A unit of angular measurement that is equal to 57.3°.

Rarefaction: An area in a material medium where the particles are less densely packed.

Real Image: An image formed by converging rays of light.

Reflection: The turning back of a wave at the boundary to the medium.

Refraction: The deflection or bending of a wave as it passes from one medium into another.

Regular Reflection: A reflection in which the reflected rays are parallel to each other.

Resistance: The opposition to the flow of electric current.

Resolution of Vectors: Breaking a vector into its components.

Rotational Equilibrium: The state of an object in which the sum of all of the clockwise and counterclockwise torques about a pivot point add up to zero.

Rotational Motion: The motion of an object that spins around an axis.

S

Scalar: A quantity that can be completely described with numbers and units.

Schematic Diagram: A drawing that shows the general layout of the elements of a circuit.

Semimajor axis: Half of the longest axis of the ellipse.

Series Circuit: An electrical circuit with only one pathway for the electric current to flow.

Specific Heat: The amount of energy required to raise the temperature of 1 gram of a substance by 1 degree Celsius.

Static Electricity: A buildup of electric charge on an object.

Static Friction: The force of friction between two objects that are not in motion relative to each other.

T

Tangential Speed: The instantaneous linear speed of an object in circular motion along the tangent to its circular path.

Torque: The ability of an applied force to produce rotational motion.

Total Internal Reflection: The reflection that occurs when light strikes the boundary to a medium at an angle of incidence that is greater than the critical angle.

Transverse Wave: A wave in which the disturbance is perpendicular to the direction of travel.

Trough: The lowest point of a wave.

U

Uniform Acceleration: See Constant Acceleration.

V

Vector: A quantity having both magnitude and direction.

Velocity: Speed in a particular direction.

Vertex: The physical center of a mirror or lens.

Virtual Image: An image that appears to be formed by diverging rays of light.

Volume: The amount of space that something occupies.

W

Wave: A set of oscillations or vibrations that transfer energy without a net transfer of mass.

Wavelength: The length of one wave cycle. The distance measured from a point on one cycle to the same point on the next cycle.

Weight: The force of attraction between two objects due to gravity.

Work: The product of the displacement and the component of the force in the direction of the displacement.