Centripetal force
The resultant force directed toward the centre of a circular path, necessary to cause centripetal acceleration and maintain circular motion: F = mv²/r = mω²r. Centripetal force is not a new type of force but the resultant of forces like tension, gravity, or friction that are directed toward the centre. Without centripetal force, the object cannot follow a circular path.
Formula
F = mv²/r = mω²r
Real World
When a roller-coaster at Alton Towers completes a vertical loop, the track's normal force and gravity together provide the centripetal force; at the top, riders feel lighter because both forces point toward the centre.
Exam Focus
At the top of a vertical loop, set mg + N = mv²/r; at the bottom, set N − mg = mv²/r — swapping these is a classic error.
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