I keep getting “Inertia” questions wrong in Laws of Motion. What's the trap?
thinking a moving body needs a continuous force to keep moving — it doesn't, unless friction acts.
The usual trap: thinking a moving body needs a continuous force to keep moving — it doesn't, unless friction acts. How to avoid it: force changes motion; it isn't needed to maintain constant velocity. Go back to the definition — the tendency of a body to resist any change in its state of rest or uniform motion (Newton's first law).
Key point
Inertia
Common mistake
thinking a moving body needs a continuous force to keep moving — it doesn't, unless friction acts.
Memory tip
force changes motion; it isn't needed to maintain constant velocity.
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