Centrina

Meet Centrina, who spins in a circle only because something keeps pulling her toward the centre.

An object moving in a circle at constant speed is still accelerating, because its direction keeps changing. That acceleration points toward the centre and has size v²/r. By Newton's second law, it needs a net inward force of mv²/r. This 'centripetal force' is not a new kind of force: it is supplied by tension, friction, gravity or whatever is doing the pulling.

Example: a 1,000 kg car taking a 50 m radius curve at 20 m/s needs 1,000 × 20² / 50 = 8,000 newtons of inward force, provided by friction between the tyres and road. Double the speed and the force needed quadruples.

Gravity supplies the centripetal force that keeps the Moon and satellites in orbit. Banked curves on roads and tracks help supply it too.

If the inward force vanishes, the object does not fly outward. It moves off in a straight line along the tangent. The outward 'centrifugal' push you feel in a turning car is a feature of describing motion from the rotating frame.