MSCE Physics flashcards

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

SI base units

Seven base units: meter, kilogram, second, ampere, kelvin, mole, candela. All other SI units derive from these by multiplication or division without numerical factors.

Random versus systematic error

Random error scatters readings unpredictably and shrinks with averaging. Systematic error shifts all readings in one direction and is corrected by calibration, not by more trials.

Precision versus accuracy

Precision is how closely repeated measurements agree with each other. Accuracy is how close a measurement is to the accepted or true value. They are independent qualities.

Falsifiability

A scientific hypothesis must make predictions that could be shown false by observation or experiment. Claims that cannot be tested in principle fall outside empirical science.

Kinematic equations

For constant acceleration: v = v0 + at, x = x0 + v0t + ½at², and v² = v0² + 2a(x − x0). These fail when acceleration changes with time.

Newton's second law

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

Static versus kinetic friction

Static friction adjusts up to a maximum μsN and prevents sliding. Kinetic friction equals μkN and opposes motion once sliding begins, usually smaller than the static maximum.

Centripetal acceleration

An object moving in a circle at constant speed accelerates toward the center with magnitude v²/r. A net inward force, such as tension or gravity, must supply it.

Work-energy theorem

The net work done on an object equals its change in kinetic energy, W_net = ½mv² − ½mv0². Work is Fd cos θ, zero when force is perpendicular to displacement.

Conservation of momentum

If no net external force acts on a system, its total momentum stays constant. Momentum is a vector, so conservation applies separately to each spatial axis.

Elastic collision

A collision in which both momentum and kinetic energy are conserved. Billiard-ball collisions approximate this; objects separate after impact rather than sticking together.

Impulse-momentum theorem

Impulse equals the change in momentum, J = FΔt = Δp. Extending collision time with the same impulse lowers the peak force, as in airbags and crumple zones.

Wave speed relation

Wave speed equals frequency times wavelength, v = fλ. Frequency is fixed by the source; crossing into a new medium changes speed and wavelength but not frequency.

Doppler effect

Observed frequency increases when source and observer approach and decreases when they recede. The shift depends on relative motion along the line joining them.

Snell's law

n1 sin θ1 = n2 sin θ2, where n = c/v is the refractive index. Light entering a higher-index medium bends toward the normal and slows down.

Total internal reflection

Occurs only when light travels from higher to lower refractive index and the incidence angle exceeds the critical angle θc = arcsin(n2/n1). No light refracts out.

Thin lens equation

1/f = 1/do + 1/di with magnification m = −di/do. Positive di gives a real image; negative di gives a virtual image on the same side as the object.

Coulomb's law

The electric force between two point charges is F = kq1q2/r², directed along the line joining them. Like charges repel and opposite charges attract.

Series versus parallel circuits

Series elements share one current and their resistances add. Parallel elements share one voltage and their conductances add, giving a smaller equivalent resistance.

Kirchhoff's rules

Junction rule: charge conservation, currents into a node sum to currents out. Loop rule: energy conservation, voltage changes around any closed loop sum to zero.

Lenz's law

An induced current flows in the direction that opposes the change in magnetic flux that produced it. This is the negative sign in Faraday's law.

Magnetic force on a charge

A charge moving in a magnetic field feels F = qvB sin θ, perpendicular to both velocity and field. A charge moving parallel to the field feels no force.

Ideal gas law

PV = nRT relates pressure, volume, moles, and absolute temperature; R ≈ 8.314 J/(mol·K). It assumes negligible molecular volume and no intermolecular forces.

First law of thermodynamics

ΔU = Q − W, where W is work done by the system. Internal energy changes by heat added minus work performed; it is a statement of energy conservation.

Carnot efficiency

The maximum possible efficiency of a heat engine is e = 1 − Tc/Th, using absolute temperatures. No real engine operating between those reservoirs can exceed it.

Root-mean-square speed

v_rms = √(3kT/m) = √(3RT/M), the typical molecular speed in an ideal gas. It rises with temperature and falls for heavier molecules.

Time dilation

A clock moving relative to an observer runs slow by Δt = γΔt0, where γ = 1/√(1 − v²/c²). The proper time Δt0 is measured in the clock's rest frame.

Photoelectric effect

Light ejects electrons only above a threshold frequency. Maximum kinetic energy is K_max = hf − φ, independent of intensity, supporting photon quantization.

de Broglie wavelength

Any particle with momentum p has wavelength λ = h/p. It is measurable for electrons and explains electron diffraction, but negligible for everyday objects.

Half-life

The time for half of a radioactive sample to decay, N = N0(1/2)^(t/T½). Decay is random per nucleus but statistically predictable for large numbers of nuclei.

Binding energy per nucleon

The energy holding a nucleus together divided by its nucleon count. It peaks near iron-56, so fusion releases energy for lighter nuclei and fission for heavier ones.

Formative versus summative assessment

Formative assessment monitors learning during instruction and guides feedback. Summative assessment evaluates achievement at the end of a unit or course.

Laser safety classes

Class 1 is safe under normal use. Class 2 visible lasers are protected by the blink reflex. Class 3B and 4 need wavelength-matched eye protection and controlled access.