Inertia, F = ma, and action-reaction pairs, with real-world examples of each law. From our 8th-grade physical-science deep-dive year — a full 10-question lesson, exactly what your child would see.
Ready for more?
Lumastery adapts to your child with interactive lessons in math, reading, science, and social studies — all built for homeschool families. Start free, no card required.
Start Free — No Card RequiredFree tier includes 1 child + 1 session per day
Inertia, F = ma, and action-reaction pairs, with real-world examples of each law. Three short rules, written more than 300 years ago, still describe how every object on Earth and in space starts moving, stops moving, and pushes back. By the end, you’ll be able to name which law is at work in everything from a braking bus to a launching rocket.
In an earlier lesson you learned how to describe motion — speed, direction, and how they change. That tells you WHAT an object is doing. But it never explained WHY. Why does a still rock stay still? Why does a hard kick send a ball farther than a gentle one? Why does a rocket move in empty space where there’s nothing to push against?
In the 1680s, Isaac Newton answered all of those questions with just three short laws describing how forces affect motion. They were so accurate that we still use them today to launch rockets, design cars, and build bridges. Together they answer three questions: why do still things stay still, how does a force change motion, and why does every push come with a push back?
You’ll meet each law one at a time, learn the math behind the second one, and then become a detective — using the three laws to crack real-world cases.
Remember the difference between speed and velocity from the motion lesson? Velocity includes both speed and direction. That word matters here, because Newton’s laws are really about changing velocity — speeding up, slowing down, OR turning. Any change in velocity is called acceleration, and you’ll see in a moment that acceleration is exactly what a force produces.