A ball is whirled in a horizontal circle of fixed radius on a string. The ball is now made to move faster around the same circle. What must happen to the pu...
Question 1 Report
A ball is whirled in a horizontal circle of fixed radius on a string. The ball is now made to move faster around the same circle. 
What must happen to the pull of the string?
Answer Details
The pull of the string must be larger. The centripetal force needed rises with speed for a fixed radius (\( F = \dfrac{mv^2}{r} \)), so moving faster around the same circle needs a bigger inward pull from the string. It cannot stay the same, because a faster ball requires more force to keep turning; it must not become smaller, which would let the ball fly outward; and it must still point inward, not outward, since the force is always towards the centre.
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