A child whirls a rubber ball on a string in a horizontal circle at speed v0 and radius r0. The child then shortens the string so that the radius becomes 21r0 while wishing to keep the magnitude of the ball’s centripetal acceleration the same as before. Which of the following is closest to the required new speed?
a) 1.41v0
b) 0.71v0
c) 0.50v0
d) 2.00v0