Moments
Why a small weight far out balances a big one close in.
The centre of mass
The one point a shape behaves as though all its weight is at.
Momentum and collisions
What is kept when things hit each other, and what is not.
Friction
The force that resists sliding, and why it does not depend on area.
Rolling and sliding
Why a ball beats a crate down a slope, and a hoop loses to both.
Energy
What is stored, what is spent, and what it turns into.
The pendulum
Why the length decides the swing and the weight does not.
Springs
A force in proportion to how far it is pulled, and what that does.
Gear ratios
Trading speed for turning force, and the price of it.
Involute teeth
The shape a gear tooth has to be, and why any other shape knocks.
The four bar linkage
Three moving bars and a frame, and everything they can trace.
The slider crank
Turning into sliding, which is every engine ever built.
The Geneva drive
Turning steadily into stopping and starting, a quarter at a time.
Ackermann steering
Why the inside wheel of a turning car points further round.
Orbits
Falling and missing, and why the far ones go slower.
Magnetism
Poles that pull and push, and steel that is pulled either way.
Materials that give
What it means for something to be soft, and what it looks like.
Trusses
Why a bridge is made of triangles and not of squares.