MTTC Physics (019) key terms

The estimated range within which the true value of a measurement lies, combining instrument resolution with variation across repeated trials. Reported with appropriate significant figures and used to judge whether two results agree.

A repeatable offset in measurements caused by faulty calibration, a zero error, or biased procedure. Unlike random error, it shifts all readings in the same direction and is not reduced by averaging more trials.

Scatter in measurements from unpredictable, uncontrolled fluctuations in instruments, environment, or observer. It has no preferred direction, and its effect on the mean shrinks as the number of trials increases.

Checking an equation by confirming that both sides carry identical base units of length, mass, time, and current. It catches algebraic mistakes and can predict the form of a relationship up to a dimensionless constant.

Rewriting a physical relationship so that plotted data fall on a straight line, such as graphing period squared against length for a pendulum. The slope and intercept then yield the constants being sought.

A quantity held constant across trials so that any change in the dependent variable can be attributed to the independent variable rather than to a competing influence.

A sketch isolating one object and drawing every external force acting on it as an arrow whose direction and relative length show orientation and magnitude, with a labeled coordinate system for components.

The net force on an object equals its mass times its acceleration, F = ma, when mass is constant. Acceleration points along the net force and is inversely proportional to mass.

The acceleration of an object moving on a curved path, directed toward the center of curvature with magnitude v squared over r. It changes the direction of velocity, not its magnitude, in uniform circular motion.

The product of a force and the time interval over which it acts; it equals the change in an object's momentum. Extending collision time with airbags or padding reduces the peak force for the same momentum change.

In a system with no net external force, total momentum stays constant through collisions and explosions. Vector addition applies, so momentum is conserved separately along each independent direction.

The net work done on an object equals its change in kinetic energy. Work by conservative forces can instead be tracked through potential energy, giving conservation of mechanical energy when only those forces act.

A body's resistance to angular acceleration, depending on its mass and how that mass is distributed about the rotation axis. It plays the role in torque equations that mass plays in F = ma.

The product of rotational inertia and angular velocity, L = I times omega. It is conserved when no net external torque acts, which explains why a spinning skater speeds up when pulling in her arms.

Oscillation in which the restoring force is proportional and opposite to displacement from equilibrium, producing sinusoidal motion. Period is independent of amplitude and set by mass and stiffness, as for a mass on a spring.

The shift in observed frequency when a source and observer have relative motion along the line joining them; approaching motion raises frequency and receding motion lowers it, for both sound and light.

The relation n1 sin theta1 = n2 sin theta2 governing refraction at an interface between media with refractive indices n1 and n2. Light bends toward the normal when entering a slower, higher-index medium.

When light travels from a higher to a lower refractive index beyond the critical angle, no light refracts out and the ray reflects entirely back into the denser medium; the basis of optical fibers and some prisms.

The spreading of waves around obstacles and through openings, becoming pronounced when the aperture is comparable to the wavelength. It sets a fundamental resolution limit for lenses and telescopes.

Superposition of waves reflected from the two surfaces of a thin layer; whether reflected light is reinforced or cancelled depends on film thickness, wavelength, and phase shifts at the interfaces.

A pattern formed by two identical waves traveling in opposite directions within a bounded region, with fixed nodes and antinodes. Allowed wavelengths are restricted by the boundary conditions.

The restriction of a transverse wave's electric field to a particular orientation. Light can be polarized by filters, by reflection at Brewster's angle, or by scattering, and transmitted intensity follows Malus's law.

A large-amplitude response occurring when a driving frequency matches a system's natural frequency. Musical instruments, tubes of air, and tuned circuits use it to select and amplify specific frequencies.

The force per unit positive charge at a point in space, a vector pointing away from positive charge and toward negative charge. Field lines are drawn denser where the field is stronger.

Potential energy per unit charge at a location, measured in volts, with the field pointing from high to low potential. Only potential differences between two points are physically measurable.

The ratio of stored charge to potential difference across a conductor arrangement, C = Q/V, measured in farads. For parallel plates it grows with plate area and decreases with plate separation.

The junction rule states that charge entering a node equals charge leaving. The loop rule states that potential changes around any closed circuit loop sum to zero. Together they solve multi-loop circuits.

A charge moving in a magnetic field experiences force qv cross B, perpendicular to both velocity and field. It does no work, so it changes direction of motion but not speed.

A changing magnetic flux through a loop induces an emf proportional to the rate of change of flux and to the number of turns. It underlies generators, transformers, and induction cooktops.

An induced current flows in the direction whose own magnetic field opposes the change in flux that produced it, a consequence of energy conservation.

The change in internal energy of a system equals heat added to it plus work done on it, under the common sign convention. Energy is conserved in every thermodynamic process.

A measure of the number of microscopic arrangements consistent with a system's macroscopic state. In isolated systems it never decreases, giving direction to spontaneous processes and limiting heat-engine efficiency.

PV = nRT relates pressure, volume, amount, and absolute temperature of a gas whose particles have negligible volume and no intermolecular forces. It follows from kinetic theory and fails near condensation.

The maximum possible efficiency of a heat engine operating between hot and cold reservoirs at absolute temperatures, 1 minus Tc/Th. Any real engine with friction and finite-time processes does worse.

Emission of electrons from a surface struck by light above a threshold frequency. It shows that light delivers energy in discrete photons, with maximum electron energy depending on frequency, not intensity.

The wavelength associated with a particle's momentum, lambda = h/p. It explains electron diffraction and why quantum effects matter for small, slow particles.

The time required for half the nuclei in a radioactive sample to decay. After n half-lives the remaining fraction is one-half raised to n, so decay is exponential rather than linear.

The relation E = mc squared stating that mass is a form of energy. Mass defects in nuclear reactions appear as released energy, which accounts for the output of fission and fusion.