An object moves in a circle.If the mass is tripled, the speed halved and the radius unchanged then the magnitude of the centripetal force must be multiplied by a factor of:
A)3/2
B)3/4
C)9/4
D)6
E)12

Question

Quizplus · Accepted Answer

The centripetal force is given by $ F = \frac{mv^2}{r} $. If the mass $ m $ is tripled and the speed $ v $ is halved, the new force is $ F' = \frac{(3m)(\frac{v}{2})^2}{r} = \frac{3m \cdot \frac{v^2}{4}}{r} = \frac{3}{4} \cdot \frac{mv^2}{r} $. Thus, the force is multiplied by a factor of $ \frac{3}{4} $.

An Object Moves in a Circle