YOUR SUBJECT LESSONS
Physics
Turn a situation into a model, with units.
- 01Sketch the system and choose an axis.
- 02Convert quantities to the units of the model.
- 03Check signs, units and the physical assumptions.
FROM PRINCIPLE TO PRACTICE
Lessons in a useful order
From foundations to high school: a mental model, worked example and four exercises with solutions per chapter.
Physics
Units: numbers have dimensions
A physical quantity combines a number and a unit.
Lesson and 4 exercisesPhysics
Electricity: voltage, current, resistance
Current is a rate of charge flow; voltage is a potential difference.
Lesson and 4 exercisesPhysics
Density and pressure
Density relates mass to volume through ρ=m/V, in kg/m³.
Lesson and 4 exercisesPhysics
Electrical power and energy
Power is energy transfer per unit time.
Lesson and 4 exercisesPhysics
Gravitation, weight and distant interaction
Masses attract gravitationally.
Lesson and 4 exercisesPhysics
Motion: position, velocity, acceleration
Position locates a system in a reference frame.
Lesson and 4 exercisesPhysics
Waves: propagate a disturbance
A wave carries a disturbance, without bulk transport of matter in the usual mechanical-wave model.
Lesson and 4 exercisesPhysics
Lenses: reconstruct an image
For a thin converging lens, a ray parallel to the axis exits through the image focus; a ray through the optical centre keeps its direction.
Lesson and 4 exercisesPhysics
Work of a force and energy balance
For constant force over straight displacement, W=Fd cos α, with angle between force and displacement.
Lesson and 4 exercisesPhysics
Forces and energy: choose the system
A force represents an interaction.
Lesson and 4 exercisesPhysics
Radioactive decay: halve each half-life
Individual decay is random.
Lesson and 4 exercisesPhysics
Ideal gas: pressure, volume and temperature
The ideal-gas model neglects particle volume and interactions outside idealised collisions.
Lesson and 4 exercisesFurther reading
Reference resources; their authors do not endorse this site.