A boy is whirling a stone around his head by means of a string. The string makes one complete revolution every second; and the magnitude of the tension in the string is F. The boy then speeds up the stone, keeping the radius of the circle unchanged, so that the string makes two complete revolutions every second. What happens to the tension in the sting?
A)The magnitude of the tension is unchanged.
B)The magnitude of the tension reduces to half of its original value, F/2.
C)The magnitude of the tension increases to twice its original value, 2F.
D)The magnitude of the tension increases to four times its original value, 4F.
E)The magnitude of the tension reduces to one-fourth of its original value, F/4.

Question

Quizplus · Accepted Answer

The tension in the string is related to the centripetal force, which depends on the square of the angular velocity. Doubling the revolutions per second quadruples the angular velocity, thus increasing the tension to four times its original value.

A Boy Is Whirling a Stone Around His Head by Means