Motion: A change in an object's position
Speed: How fast an object moves: distance divided by time
Velocity: Speed in a given direction
Acceleration: How quickly velocity changes
Displacement: The straight-line change in position, with direction
Distance: The total length of the path traveled
Scalar: A quantity with size only, like speed
Vector: A quantity with size and direction, like velocity
Force: A push or a pull
Net force: The total of all forces acting on an object
Balanced forces: Forces that cancel, causing no change in motion
Unbalanced forces: Forces that do not cancel, causing a change in motion
Inertia: An object's resistance to change in its motion
Mass: The amount of matter in an object
Weight: The force of gravity on an object
Gravity: The force that pulls objects with mass toward each other
Friction: A force that resists sliding between surfaces
Air resistance: Friction from air pushing against a moving object
Terminal velocity: The constant speed reached when air resistance equals weight
Momentum: Mass times velocity
Impulse: A force applied over time, changing momentum
Work: Force applied over a distance
Power: The rate of doing work
Energy: The ability to do work or cause change
Kinetic energy: Energy of motion
Potential energy: Stored energy due to position or condition
Gravitational potential energy: Energy stored in an object because of its height
Elastic potential energy: Energy stored in stretched or squeezed objects
Thermal energy: The total kinetic energy of the particles in an object
Heat: Thermal energy moving from hot to cold
Temperature: A measure of the average kinetic energy of particles
Conduction: Heat moving through direct contact
Convection: Heat moving by the flow of fluids
Radiation: Energy traveling as waves, even through empty space
Wave: A disturbance that carries energy
Frequency: The number of waves passing a point per second
Wavelength: The distance from one wave crest to the next
Amplitude: The height of a wave from its rest position
Hertz: The unit of frequency: one wave per second
Reflection: Waves bouncing off a surface
Refraction: Waves bending when they enter a new material
Diffraction: Waves spreading as they pass an edge or opening
Absorption: A material taking in wave energy
Transverse wave: A wave in which particles move up and down across the wave's direction
Longitudinal wave: A wave in which particles move back and forth along the wave's direction
Electromagnetic spectrum: The full range of light waves from radio to gamma rays
Circuit: A closed path for electric current
Current: The flow of electric charge
Voltage: The push that moves charge through a circuit
Resistance: How much a material opposes electric current
Conductor: A material that carries electricity or heat well
Insulator: A material that carries electricity or heat poorly
Magnet: An object that attracts iron and has two poles
Magnetic field: The area around a magnet where it exerts force
Electromagnet: A magnet made by passing current through a coil of wire
Static electricity: A buildup of electric charge on an object
Atom: The smallest unit of an element
Nuclear fission: Splitting a large nucleus into smaller ones, releasing energy
Nuclear fusion: Joining small nuclei into a larger one, releasing energy
Radioactive decay: An unstable nucleus giving off particles or energy
Pressure: Force per unit area
Buoyancy: The upward push of a fluid on an object
Density: Mass per unit of volume
Torque: A twisting force
Centripetal force: A force that pulls an object toward the center of a circle
Projectile: An object thrown or launched and moving under gravity
Free fall: Falling with only gravity acting
Efficiency: The share of input energy that does useful work

Free flashcards from Peabody at peabody.kids/flashcards/phys-terms