An object moves around a circle.If the radius is doubled keeping the speed the same then the magnitude of the centripetal force must be:
A)twice as great
B)half as great
C)four times as great
D)one-fourth as great
E)the same

Question

Quizplus · Accepted Answer

The centripetal force required to keep an object moving in a circle is given by $F = \frac{mv^2}{r}$, where $m$ is the mass, $v$ is the velocity, and $r$ is the radius of the circle. If the radius is doubled ($r$ becomes $2r$) and the speed remains the same, the new force is $F' = \frac{mv^2}{2r}$, which is half the original force. Therefore, the magnitude of the centripetal force must be half as great.

An Object Moves Around a Circle