A ball is whirled in a horizontal circle of radius r and speed v.The radius is increased to 2r keeping the speed of the ball constant.The period of the ball changes by a factor of
A)half
B)one
C)two
D)three
E)four

Question

Quizplus · Accepted Answer

The period of a circular motion is determined by the time it takes for the object to complete one full revolution. Since the speed of the ball remains the same, the only change is in the radius. 
Using the formula for period of circular motion, T = 2πr/v, 
when the radius is doubled, the period becomes T' = 2π(2r)/v = 4πr/v 
Therefore, T' is twice the initial period T. 
Hence, the correct answer is (C) two.

A Ball Is Whirled in a Horizontal Circle of Radius