Key idea
Circular motion
a_c = v²/r = ω²r · F_c = mv²/r
Start with the central idea, then test it against a concrete element or example. A scientific model is useful when we know what it explains — and where its limits are.
Circular motion
The key idea
Motion along a circle requires an acceleration directed toward the centre whenever speed is nonzero, even if the speed’s magnitude stays constant.
Why it matters
Changing direction is already acceleration; a force balance must provide the required centripetal acceleration.
A picture to remember
Key idea
Circular motion
Guided example
Circular motion
Start with the central idea, then test it against a concrete element or example. A scientific model is useful when we know what it explains — and where its limits are.
Put it into practice
Circular motion
Choose a concrete case linked to Circular motion. Write down the known information, what you are trying to find, and the units. Then state the rule, model or trend you will use. If a calculation is involved, keep the units visible at every line; if it is conceptual, state what changes and what remains fixed.
Check your answer
A strong answer contains four things: the starting situation, the variable that changes, the direction or numerical result, and one check. The check can be a unit, an order of magnitude, a limiting case or a comparison with a familiar example.