A girl twirls a key chain in a circle if she twirls it faster, she finds that she holds the chain tighter. Explain why this is necessary.
I think it's that she has to hold the chain tighter because there is more velocity and force.
Is this right? Explain further using physics terms
You are pretty much right:)
Actually, she's creating the centripetal force (F) in order make the chain move by a circle.
If R is the radius of that circle, and V is the speed of movement,
[this can be analyzed in details, but we need the sketch of this activity; consider V as an effective speed]
then the force is,
F=mv^2/R , with m being the mass of chain.
R directed into the center of "twirling", and, it's provided by the "girl" [say, her fingers ...].
So, the faster she rotates the chain, the bigger force is needed to secure the circular motion ...
Even, you may see, that the force strongly depends on V - it's quadratic dependence.
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