Level 5: Newton's laws

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

In this level you meet the three laws Isaac Newton published in 1687, which explain almost all the motion you will ever see. You learn what inertia is and why mass measures it, use \(F = ma\) and \(W = mg\) on Mars and on Earth, find the pairs of forces in the third law, and draw free-body diagrams, the tool every engineer uses to solve a force problem.

Lesson	You will be able to
The first law	State Newton's first law and use it to explain seat belts and coasting spacecraft
Mass and inertia	Explain why mass measures inertia, and how astronauts weigh themselves in orbit
The second law, F = ma	Use \(F = ma\) to find a force, a mass or an acceleration
Weight is a force, W = mg	Find weights on Mars and Earth, and explain why everything falls at the same rate
The third law	Find the pair of forces in any interaction, and say which objects they act on
Free-body diagrams	Draw the forces on one object and use them with \(F = ma\)

Previous: Level 4: Speed and direction · Next: Level 6: Friction and slopes · Forces and motion topic page · The companion level: Rockets, level 5