Physics 30

A strong investigation starts with a narrow, testable question and a hypothesis that predicts a measurable outcome.

The experimental design names the variables, controls, procedure, and safety considerations before any data is collected.

Running the experiment means following the planned protocol carefully, recording data systematically, and repeating trials for reliability.

Analysis turns raw data into meaning - tables, graphs, and calculations that let you judge whether the hypothesis was supported.

A portfolio gathers the question, method, data, analysis, and conclusion into a clear story others can follow.

Newtonian mechanics describes everyday objects well; quantum mechanics governs the atomic and subatomic scale; relativity governs the very fast and very massive.

Alpha, beta, and gamma radiation differ in composition, charge, penetrating power, and potential danger.

Each theory is a powerful model within its domain, and the search continues for a theory that unifies them.

Radiation comes from natural sources (rocks, cosmic rays) and artificial ones (medical, industrial), and different types are stopped by different materials.

Special relativity deals with constant-velocity motion near the speed of light, predicting time dilation, length contraction, and relativistic mass.

Uniform motion has constant velocity; uniformly accelerated motion has constant acceleration, described by the kinematics equations.

Newton's laws relate force to motion: inertia (first law), F = ma (second law), and action-reaction pairs (third law).

Motion graphs (position-time, velocity-time) and the kinematics equations give two consistent ways to solve for an unknown.

A free-body diagram isolates all forces on an object so the net force and resulting acceleration can be found.

A projectile's horizontal motion is uniform while its vertical motion is uniformly accelerated by gravity; the two are independent.

Work is the energy transferred when a force acts over a displacement; mechanical energy is the sum of kinetic and gravitational potential energy.

Momentum is mass times velocity; impulse is force times the time it acts, and impulse equals the change in momentum.

In an isolated system total mechanical energy is conserved, so energy transforms between kinetic and potential without loss.

Extending the time over which a force acts reduces the force needed for a given momentum change - the physics behind airbags and crumple zones.

Efficiency is the ratio of useful energy output to total energy input; no real machine is 100% efficient.

A field represents a non-contact force (action at a distance); gravitational field strength gives the force per unit mass at a point.

An electric field surrounds any charge; field lines point away from positive and toward negative charges, and field strength follows an inverse-square law.

Mass is the amount of matter (unchanging); weight is the gravitational force on that mass, which varies with field strength.

Coulomb's law, F = k q1 q2 / d^2, gives the force between two point charges.

Gravitational field strength follows an inverse-square law: g = GM/r^2, so it weakens rapidly with distance.