Georgia Unified Physics flashcards

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

Centripetal acceleration

For an object moving in a circle of radius r at speed v, acceleration has magnitude v²/r and points toward the center; it changes direction, not speed.

Impulse-momentum theorem

The impulse delivered to an object equals its change in momentum: FΔt = Δp. A longer collision time with the same impulse means a smaller average force.

Conservation of mechanical energy

When only conservative forces act, KE + PE stays constant. Falling objects trade gravitational potential energy mgh for kinetic energy ½mv², so v = √(2gh) from rest.

Static versus kinetic friction

Static friction adjusts up to μ_sN to prevent sliding; kinetic friction equals μ_kN while sliding. Because μ_s exceeds μ_k, starting motion takes more force than keeping it.

Torque

Torque about a pivot is τ = rF sinθ, where θ is the angle between the lever arm and the force. Maximum torque occurs when force is perpendicular to the lever arm.

First law of thermodynamics

ΔU = Q − W, where Q is heat added to the system and W is work done by the system. For an isochoric process W = 0, so ΔU equals Q.

Carnot efficiency limit

No heat engine operating between reservoirs at T_H and T_C can exceed e = 1 − T_C/T_H. Temperatures must be in kelvin, and real engines fall below this ceiling.

Latent heat

Energy absorbed or released during a phase change at constant temperature is Q = mL, where L is the specific latent heat. No temperature change occurs during melting or boiling.

Adiabatic process

A process with no heat exchange, Q = 0, so the first law gives ΔU = −W. Compressing a gas adiabatically raises its temperature; expanding it adiabatically cools it.

Standing waves on a string

Both ends fixed gives nodes at each end, so wavelengths are λ = 2L/n and frequencies f = nv/(2L). The n = 1 mode is the fundamental.

Total internal reflection

Occurs when light travels from a higher to a lower index and the incident angle exceeds the critical angle θ_c = sin⁻¹(n₂/n₁). The interface then reflects all light.

Snell's law

n₁sinθ₁ = n₂sinθ₂, with n = c/v for each medium. Entering a higher-index medium slows light and bends it toward the normal.

Thin lens equation

1/f = 1/d_o + 1/d_i with magnification m = −d_i/d_o. A negative image distance for a lens means a virtual image on the object side.

Double-slit interference

Constructive interference occurs at d sinθ = mλ for integer m, producing bright fringes. Increasing slit separation d decreases fringe spacing on the screen.

Ohm's law

V = IR for an ohmic conductor at constant temperature. Power dissipated follows P = IV = I²R = V²/R, so doubling current quadruples resistive power loss.

Parallel resistors

The reciprocal of equivalent resistance is the sum of reciprocals: 1/R_eq = 1/R₁ + 1/R₂. Equivalent resistance is always less than the smallest individual resistor.

Kirchhoff's loop rule

Around any closed loop, the sum of potential changes is zero. This expresses energy conservation: charges returning to a point must have the same potential.

Magnetic force on a charge

F = qvB sinθ, perpendicular to both velocity and field. Because force is perpendicular to motion, magnetic fields do no work and cannot change speed.

Faraday's law of induction

Induced emf equals the negative rate of change of magnetic flux through a loop: ε = −NΔΦ/Δt. Faster flux change or more turns yields larger emf.

Electric field of a point charge

E = kq/r², directed away from positive charge and toward negative charge. Field magnitude falls off as the inverse square of distance.

Photoelectric effect

Electrons are ejected only when photon energy hf exceeds the work function φ. Maximum kinetic energy is K_max = hf − φ; intensity affects count, not energy.

de Broglie wavelength

Any particle with momentum p has wavelength λ = h/p. Electrons at typical laboratory speeds have wavelengths comparable to atomic spacing, enabling diffraction.

Half-life

The time for half of a radioactive sample to decay. After n half-lives, the remaining fraction is (1/2)ⁿ, and activity decreases by the same factor.

Mass defect and binding energy

A nucleus is lighter than its separated nucleons by Δm; the binding energy is Δm·c². Binding energy per nucleon peaks near iron-56, the most stable region.

Alpha decay

A nucleus emits a helium-4 nucleus, decreasing mass number by 4 and atomic number by 2. The daughter element sits two places left in the periodic table.

Hydrogen energy levels

E_n = −13.6 eV/n², with n = 1 the ground state. A photon is emitted when an electron drops to a lower level, carrying exactly the energy difference.

Percent error

Percent error = |measured − accepted|/|accepted| × 100, comparing a result to an accepted value. It is not the same as percent difference between two measurements.

Linearizing a graph

Plot a transformed variable so the relationship becomes a straight line, then use the slope to extract a constant. Example: T² versus L for a pendulum gives slope 4π²/g.

Random versus systematic error

Random error scatters readings in both directions and shrinks with averaging. Systematic error shifts all readings in one direction and is not reduced by averaging.

Propagating uncertainty

For adding or subtracting, add absolute uncertainties. For multiplying or dividing, add fractional uncertainties, then convert back to an absolute uncertainty.

Significant figures in operations

Multiplication and division results keep the fewest significant figures among inputs. Addition and subtraction results keep the fewest decimal places among inputs.

Control of variables

Only the independent variable is changed while all others are held constant, so any effect on the dependent variable can be attributed to the independent variable.