Level 5: Newton's laws for rockets

Rockets and landing · level 5 of 8 · rough age 12-13 (a guide for parents; anyone can start anywhere)

This level turns the ideas of levels 1 to 4 into equations. You use Newton's second law, \(F = ma\), for rockets, landers and rovers; compare thrust with weight on two planets; meet momentum and impulse, which explain soft landings; find a rocket's thrust from the speed and flow of its exhaust; and put a number on drag.

Lesson	You will be able to
F = ma	State Newton's three laws and use \(F_\text{net} = ma\) with free-body diagrams
Thrust-to-weight ratio	Find a rocket's starting acceleration from its thrust-to-weight ratio, on Earth and on Mars
Momentum	Use \(p = mv\), and compare the momentum of rovers, rockets and exhaust
Impulse	Use \(F\,\Delta t = \Delta p\) to find landing forces, and explain why a longer stop is gentler
Exhaust speed	Use thrust \(= \dot m\, v_e\) to link an engine's thrust, propellant flow and exhaust speed
Drag and speed	Use \(F = \tfrac12\rho v^2 C_d A\) and dynamic pressure to find max Q

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