AEPA Physics (NT308) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Newton's second law

The net force on an object equals its mass times its acceleration, so acceleration is directly proportional to net force and inversely proportional to mass.

Conservation of momentum

In an isolated system with no external net force, the total momentum before an interaction equals the total momentum after it, in every collision type.

Centripetal acceleration

An object moving in a circle of radius r at speed v accelerates toward the center with magnitude v squared divided by r, changing direction but not speed.

Archimedes' principle

The buoyant force on an object in a fluid equals the weight of the fluid it displaces, explaining why less dense objects float.

Hooke's law

The restoring force of an ideal spring is proportional to its displacement from equilibrium and directed opposite to that displacement, with constant k.

Coulomb's law

The electrostatic force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation.

Ohm's law

For an ohmic conductor at constant temperature, current is directly proportional to voltage and inversely proportional to resistance, written V equals I R.

Kirchhoff's junction rule

The sum of currents entering a circuit junction equals the sum leaving it, a direct consequence of conservation of electric charge.

Faraday's law of induction

A changing magnetic flux through a loop induces an emf proportional to the rate of change of that flux, and to the number of turns.

Lenz's law

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

Magnetic force on a charge

A charge moving through a magnetic field experiences a force perpendicular to both its velocity and the field, proportional to charge, speed, and field strength.

Capacitor energy storage

The energy stored in a charged capacitor equals one half the capacitance times the square of the voltage across its plates.

Wave equation

For any periodic wave, speed equals frequency multiplied by wavelength; frequency is fixed by the source while speed and wavelength depend on the medium.

Snell's law

At an interface, the product of refractive index and sine of the angle from the normal is the same on both sides of the boundary.

Total internal reflection

Light traveling from a higher to a lower index medium reflects entirely at the boundary when its angle exceeds the critical angle.

Thin lens equation

The reciprocal of focal length equals the sum of the reciprocals of object and image distances, with magnification equal to negative image distance over object distance.

Doppler effect

The observed frequency of a wave shifts upward when source and observer approach and downward when they recede, due to relative motion.

Double-slit interference

Bright fringes appear where light from two slits arrives in phase, at path differences equal to whole-number multiples of the wavelength.

First law of thermodynamics

The change in internal energy of a system equals heat added to it minus work done by it, expressing conservation of energy.

Second law of thermodynamics

Spontaneous processes increase the total entropy of an isolated system, so heat flows from hot to cold and no engine is perfectly efficient.

Ideal gas law

Pressure times volume equals the number of moles times the gas constant times absolute temperature for an ideal gas.

Carnot efficiency

The maximum efficiency of a heat engine equals one minus the ratio of cold reservoir temperature to hot reservoir temperature, both in kelvin.

Latent heat

The energy absorbed or released per unit mass during a phase change, occurring at constant temperature while bonds rearrange.

Photoelectric effect

Light ejects electrons from a metal only above a threshold frequency; maximum electron kinetic energy depends on frequency, not on light intensity.

de Broglie wavelength

Every particle has an associated wavelength equal to Planck's constant divided by its momentum, observable for electrons and other small masses.

Radioactive half-life

The time required for half the nuclei in a radioactive sample to decay, giving an exponential decrease in activity over time.

Mass-energy equivalence

Mass and energy are interchangeable, related by energy equals mass times the speed of light squared; mass defect appears as released nuclear energy.

Independent and dependent variables

The independent variable is deliberately changed by the experimenter, while the dependent variable is measured to reveal the effect of that change.

Accuracy versus precision

Accuracy is closeness to the accepted value; precision is closeness of repeated measurements to one another, independent of the true value.

Systematic versus random error

Systematic error shifts all measurements in one direction and requires calibration; random error scatters results and is reduced by averaging trials.

Significant figures

The digits in a measurement that carry meaning about its precision, limiting how precisely a calculated result may be reported.

Hypothesis

A testable, falsifiable proposed explanation for an observation, stated so that predictions can be checked against experimental evidence.