Inertia, Interaction of Bodies and Mass
Why a moving thing keeps going, and what "mass" really measures
Big Idea: A body does not change its speed by itself. To speed it up, slow it down, or turn it, another body has to act on it. Some bodies are hard to speed up or stop — we say they have more inertness, and we measure that inertness with a number called mass.
By the end of this topic you will be able to:
- explain what inertia is and give everyday examples;
- tell the difference between inertia and inertness;
- describe how bodies change each other's speed in an interaction;
- use mass as the measure of a body's inertness;
- compare masses from an interaction and measure mass with a balance.