Physics / core
Build and test mechanical models
Develop reliable Newtonian models for constrained motion, friction, drag, variable mass, and central forces, with explicit validity checks.
Your route through physics
Follow the path or begin with a question. Every lesson is open.
Your place, at your pace. Progress is optional and saved only in this browser when available.
Read / explore / reason
Inside this module
Module 01 core
Build and test mechanical models
Develop reliable Newtonian models for constrained motion, friction, drag, variable mass, and central forces, with explicit validity checks.
- 01
Free-body diagrams begin with a boundary
Choose a mechanical system, distinguish external interactions from internal forces, and test a diagram against measured acceleration.
29 min - 02
Constraints determine motion; reactions enforce them
Translate rope lengths and contact geometry into acceleration relations, then solve for tensions without assuming every pulley is ideal.
31 min - 03
Friction is a branch decision
Use the static-friction inequality before a sliding law, determine the direction from relative slip, and recognize where Coulomb friction stops being predictive.
30 min - 04
Choose a drag law by its regime
Compare linear and quadratic resistance through relative fluid velocity, dimensional coefficients, terminal speed, and experimentally testable scaling.
33 min - 05
Projectiles with drag need velocity-dependent acceleration
Solve the linear-drag projectile exactly, explain quadratic component coupling, and locate landing events without reusing vacuum formulas.
34 min - 06
Accelerating coordinates require inertial-force terms
Transform Newton's equation between inertial and accelerating frames, then distinguish translational, centrifugal, Coriolis, and Euler terms.
34 min - 07
Coriolis deflection depends on relative velocity
Predict Coriolis directions with a cross product, estimate short-time deflection, and distinguish coordinate curvature from an energy source.
33 min - 08
Rocket thrust comes from momentum flow
Derive the variable-mass equation with an explicit exhaust convention, integrate the ideal rocket equation, and distinguish thrust from external environmental forces.
35 min - 09
An effective potential organizes central-force motion
Reduce a central-force orbit to radial motion at fixed angular momentum, locate turning points, and distinguish stable circular motion from escape.
35 min - 10
Kepler geometry and time-averaged energy
Relate two-body inverse-square motion to orbital elements, the vis-viva equation, and the bounded-motion assumptions behind the virial relation.
36 min