Centripetal Force Penny – Sick Science! #157
Find out how this works at: http://www.stevespanglerscience.com/lab/experiments/centripetal-force-penny
As a penny balances precariously on the hook of a wire hanger, you might think any sort of movement would send the penny flying. With a bit of physics know-how, you can spin the entire hanger around in a circle without losing the 1? coin. When it comes down to it, you just need to thank Sir Isaac Newton.
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The finger is the point of gravity creating centripetal force like a protoplanetary disc
You should do the same trick but with a cup of water it works also
Centripetal 'force' is not a force at all, but simply a measure of the tension that's exerted along the length of the coat hanger wires as a result of centrifugal 'force' which also is not a force, but the result of entropy – as a body in motion or at rest 'without interference' will continue to move or remain at rest.
In this case the circular path causes interference to the objects normal path of motion, causing the centrifugal 'force' and so on.
Friction between the penny and the end of the wire also plays a part, otherwise even the slightest change in momentum would cause the penny to slide off the end of the wire.
Inertia
This is not Centripetal force at all. It is centrifugal just like a centrifuge, the same exact principle. Centripetal force is inward directed thrusting force, aka implosion! Not a pulling force, which is what you are doing by swinging the hanger.
Center force