A Boy on a Bicycle Rides in a Circle of Radius

Multiple Choice

A boy on a bicycle rides in a circle of radius $r_{0}$ at speed $v_{0}$ . If the boy now rides at a radius equal to half the initial radius $r_{\mathrm{o}}$ , by what approximate factor must he change his speed in order to have the same radial acceleration?

A) 0.25
B) 2
C) 0.71
D) 4
E) 0.5
F) 1.4