A 10g bead is attached to a light string and whirls in a horizontal circle of radius 5.0cm about a vertical axis through the circle’s center. What is the bead’s rotational inertia about that axis?
a) 5.0×10−4kg⋅m2
b) 2.5×10−3kg⋅m2
c) 1.25×10−5kg⋅m2
d) 2.5×10−5kg⋅m2