NYSTCE Physics flashcards

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

SI base units

The seven SI base units are kilogram, meter, second, ampere, kelvin, mole, and candela; derived units are formed by multiplication or division of these base units.

Accuracy versus precision

Accuracy describes how close a measurement is to the accepted value; precision describes how closely repeated measurements agree with one another, regardless of closeness to the accepted value.

Random versus systematic error

Random error varies unpredictably between trials and is reduced by averaging; systematic error shifts measurements consistently in one direction and is not reduced by averaging, requiring calibration or correction.

Dimensional analysis check

Both sides of a valid physical equation must have identical dimensions. Convert quantities to base dimensions and compare; an equation whose dimensions differ cannot be correct.

Kinematic equation no time

For constant acceleration, v squared equals initial velocity squared plus twice acceleration times displacement: v² = v₀² + 2aΔx. It relates velocities, acceleration, and displacement without elapsed time.

Newton's second law

The net external force on an object equals its mass times acceleration, F_net = ma. Acceleration is in the same direction as the net force and inversely proportional to mass.

Static versus kinetic friction

Static friction adjusts up to a maximum μ_sN to prevent sliding; kinetic friction equals μ_kN and opposes motion while an object slides. Usually μ_s exceeds μ_k for the same surfaces.

Work-energy theorem

The net work done on an object equals its change in kinetic energy: W_net = ΔK = ½mv_f² − ½mv_i². Work by conservative forces can instead be represented as negative potential-energy change.

Conservation of momentum

If the net external force on a system is zero, total momentum remains constant. For collisions, initial total momentum equals final total momentum; kinetic energy is conserved only in elastic collisions.

Centripetal acceleration

For uniform circular motion, centripetal acceleration has magnitude v²/r and points toward the circle's center. The required centripetal force equals mv²/r and is not a separate new force.

Orbital speed

For a circular orbit of radius r around a body of mass M, orbital speed equals the square root of GM/r. The orbiting object's mass cancels and does not affect the speed.

Ideal gas law

PV = nRT relates pressure, volume, amount in moles, and absolute temperature for an ideal gas; R is the universal gas constant. Temperature must be in kelvin for the equation to work.

First law of thermodynamics

The change in internal energy of a system equals heat added to the system minus work done by the system: ΔU = Q − W. Energy is conserved and internal energy is a state function.

Specific heat capacity

The heat needed to change an object's temperature is Q = mcΔT, where m is mass, c is specific heat, and ΔT is temperature change. No phase change occurs during this calculation.

Latent heat

During a phase change at constant temperature, heat transferred is Q = mL, where L is the latent heat of fusion or vaporization. Temperature remains constant while the phase change proceeds.

Carnot efficiency

The maximum theoretical efficiency of a heat engine operating between hot and cold reservoirs is η = 1 − T_c/T_h, with temperatures in kelvin. No real engine exceeds this limit.

Wave speed relation

For any periodic wave, speed equals frequency times wavelength: v = fλ. Frequency is set by the source, while speed and wavelength depend on the medium.

Doppler effect

The observed frequency increases when source and observer approach and decreases when they recede. The shift depends on relative motion and the wave speed in the medium.

Snell's law

Refraction at an interface obeys n₁ sin θ₁ = n₂ sin θ₂, where n is the refractive index and angles are measured from the normal. Light bends toward the normal when entering a higher-index medium.

Total internal reflection

Total internal reflection occurs when light travels from a higher-index to a lower-index medium and the incidence angle exceeds the critical angle, given by sin θ_c = n₂/n₁.

Thin lens equation

The thin lens equation is 1/f = 1/d_o + 1/d_i, where f is focal length and object and image distances follow a sign convention. Magnification is m = −d_i/d_o.

Double-slit interference

For two coherent slits separated by distance d, constructive interference occurs at angles satisfying d sin θ = mλ, where m is an integer and λ is wavelength.

Coulomb's law

The electric force between two point charges is F = k|q₁q₂|/r², directed along the line joining them. Like charges repel, opposite charges attract, and k is Coulomb's constant.

Ohm's law

For an ohmic conductor at constant temperature, current equals voltage divided by resistance: I = V/R. Resistance depends on material and geometry, not directly on voltage for ohmic behavior.

Series versus parallel resistors

In series, resistances add: R_eq = R₁ + R₂ + …; the same current passes through each. In parallel, reciprocal resistances add: 1/R_eq = 1/R₁ + 1/R₂ + …; voltage is the same.

Capacitance

Capacitance is charge stored per unit voltage: C = Q/V. A parallel-plate capacitor has C = ε₀A/d, and stored energy is U = ½CV².

Magnetic force on charge

A charge q moving with velocity v in magnetic field B experiences force F = qv × B. The force is perpendicular to both velocity and field and does no work on the charge.

Faraday's law

A changing magnetic flux through a loop induces an emf equal to ε = −N ΔΦ/Δt. Lenz's law says the induced current opposes the change in flux that produced it.

Photoelectric effect

Light ejects electrons from a metal only if photon energy hf exceeds the work function φ. Maximum kinetic energy is K_max = hf − φ, independent of light intensity.

de Broglie wavelength

Matter waves have wavelength λ = h/p, where h is Planck's constant and p is momentum. Higher momentum corresponds to a shorter wavelength.

Time dilation

A clock moving relative to an observer runs slow: Δt = γΔτ, where γ = 1/√(1 − v²/c²) and Δτ is proper time measured by the moving clock.

Half-life

After n half-lives, the remaining radioactive nuclei equal N₀(1/2)^n. Half-life is the time for half of the original radioactive nuclei to decay, independent of initial amount.