MTLE Physics (Grades 9-12) flashcards

31 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 acceleration (ΣF = ma); acceleration points in the direction of the net force and is inversely proportional to mass.

Static vs kinetic friction

Static friction adjusts up to a maximum μsN to prevent sliding, while kinetic friction has the fixed value μkN and opposes motion already occurring; μs usually exceeds μk.

Elastic collision

A collision in which both total momentum and total kinetic energy are conserved; billiard-ball collisions approximate this ideal when deformation energy is fully returned.

Perfectly inelastic collision

A collision in which the objects stick together and move with one common velocity; momentum is conserved but the maximum possible kinetic energy is lost to internal energy.

Centripetal acceleration

Acceleration of magnitude v²/r directed toward the center of a circular path; it changes only the direction of velocity, never the speed, and requires a net inward force.

Projectile motion components

Horizontal and vertical motions are independent; horizontal velocity stays constant while vertical acceleration is g downward, so time of flight depends only on vertical displacement and initial vertical velocity.

Work-energy theorem

The net work done on an object equals its change in kinetic energy; work by nonconservative forces such as friction changes total mechanical energy.

Conservation of mechanical energy

When only gravity and ideal springs do work, the sum of kinetic and potential energy stays constant, allowing speed to be found from height or spring compression.

Universal gravitation

Every pair of masses attracts with force F = Gm₁m₂/r², directed along the line joining their centers; G ≈ 6.67 × 10⁻¹¹ N·m²/kg².

Torque

Torque equals rF sinθ, where θ is the angle between the lever arm and force; it is maximal when the force is perpendicular to the lever arm and zero when parallel.

Angular momentum conservation

If the net external torque on a system is zero, its angular momentum L = Iω remains constant, so reducing the moment of inertia increases angular velocity.

Simple pendulum period

For small angles, T = 2π√(L/g); the period depends on length and gravitational field strength but not on the bob's mass or, for small swings, on amplitude.

Mass-spring period

A mass on an ideal spring oscillates with T = 2π√(m/k); a stiffer spring shortens the period and a larger mass lengthens it, independent of amplitude.

Wave speed relation

Wave speed equals frequency times wavelength (v = fλ); when a wave enters a new medium, frequency stays fixed while speed and wavelength change together.

Standing wave nodes

Nodes are points of zero displacement spaced half a wavelength apart; fixed boundaries force nodes and free boundaries force antinodes, setting allowed harmonic frequencies.

Ohm's law

For an ohmic conductor at constant temperature, current is proportional to voltage: V = IR, where R is resistance in ohms and I is current in amperes.

Series circuit rules

Current is the same through every element; voltages add to the source voltage; equivalent resistance is the sum of individual resistances, so adding resistors increases total resistance.

Parallel circuit rules

Voltage is the same across each branch; branch currents sum to the total current; equivalent resistance is less than the smallest branch resistance because 1/Req = Σ1/Ri.

Coulomb's law

The electric force between point charges is F = kq₁q₂/r², attractive for opposite signs and repulsive for like signs; k ≈ 8.99 × 10⁹ N·m²/C².

Magnetic force on moving charge

F = qvB sinθ, directed perpendicular to both velocity and magnetic field by the right-hand rule; a charge moving parallel to the field feels no magnetic force.

Electromagnetic induction

A changing magnetic flux through a loop induces an emf; Faraday's law gives emf = −NΔΦ/Δt and Lenz's law says the induced current opposes the change in flux.

Snell's law

n₁ sinθ₁ = n₂ sinθ₂ describes refraction at an interface; light bends toward the normal when entering a higher-index medium and away when exiting it.

Total internal reflection

Occurs when light travels from higher to lower index at an angle exceeding the critical angle, where sinθc = n₂/n₁; no refracted ray exists beyond that angle.

Ideal gas law

PV = nRT relates pressure, volume, moles, and absolute temperature; R ≈ 8.31 J/(mol·K) and temperature must be expressed in kelvin, not Celsius.

First law of thermodynamics

ΔU = Q − W, where W is work done by the system; internal energy rises with heat added and falls when the system does work on its surroundings.

Buoyant force

Archimedes' principle: the buoyant force equals the weight of displaced fluid, F = ρfluid Vsubmerged g; a floating object displaces fluid equal to its own weight.

Hydrostatic pressure

Absolute pressure at depth h is P = P₀ + ρgh; gauge pressure ρgh depends only on depth and fluid density, not on container shape or total volume.

Half-life

The time for half the radioactive nuclei in a sample to decay; after n half-lives the remaining fraction is (1/2)ⁿ, and decay rate falls by the same fraction.

Photoelectric effect

Electrons are ejected only if incident photon energy hf exceeds the work function φ; maximum kinetic energy equals hf − φ, and intensity affects current but not maximum energy.

Photon energy

A photon carries energy E = hf = hc/λ; shorter wavelength means higher energy, and h ≈ 6.63 × 10⁻³⁴ J·s.

Special relativity time dilation

A clock moving at speed v relative to an observer runs slow by factor γ = 1/√(1 − v²/c²); the effect is negligible at ordinary speeds and grows near light speed.