Level 8: Rotation and stress

Forces and motion · level 8 of 8 · rough age 17 and beyond (a guide for parents; anyone can start anywhere)

In this level forces make things turn and stretch. You meet torque, moment of inertia and the turning form of Newton's second law, use the conservation of angular momentum on a skater, a spinning habitat and the planet Mars itself, and learn the language of stress and strain. It ends with a surprise for anyone building on Mars: the biggest load on a habitat is not its weight but the air inside it.

Lesson	You will be able to
Torque	Find the turning effect of a force, and explain why undoing a bolt is harder on Mars
Moment of inertia	Find moments of inertia and use them to race rolling objects down a slope
Turning faster: τ = Iα	Use the rotational second law for wheels and flywheels
Angular momentum	Use conservation of angular momentum, from skaters to the spin of Mars
Stress and strain	Use stress, strain and Young's modulus to size a cable or a column
Building under 0.38 g	Compare the weight loads and pressure loads on a Mars habitat

Previous: Level 7: Moving in circles · Forces and motion topic page · The companion level: Rockets, level 8