Forces and motion

Everything that starts, stops, turns or speeds up does so because of a force. This topic starts with pushing toys across the floor and climbs to Newton's three laws, friction, and the forces that hold a rover on a slope or a habitat's spinning wheel together. On Mars the same laws hold; only the numbers change.

8 levels. The ages are only a rough guide for parents and teachers; anyone can start at any level.

Level	Rough age	What it covers
Level 1: Pushes and pulls	5-6	Pushing, pulling, starting and stopping; heavy things are harder to move
Level 2: Rubbing and rolling	7-8	Friction, wheels, slopes, why a rover drives slowly on sand
Level 3: Balanced and unbalanced	9-10	Force arrows, balanced forces, the newton, springs that measure force
Level 4: Speed and direction	11-12	Speed, velocity, distance-time graphs, why turning needs a force
Level 5: Newton's laws	12-13	Inertia, F = ma, action and reaction, free-body diagrams
Level 6: Friction and slopes	13-14	Coefficients of friction, forces on a ramp, a rover parked on a 30° slope on Mars
Level 7: Moving in circles	15-16	Centripetal force, banked tracks, spinning a habitat for artificial gravity
Level 8: Rotation and stress	17 and beyond	Torque, moments of inertia, angular momentum, the strength of materials under 0.38 g