[填空题]
A ball on the end of a qki; -ox h p(i rlq)tc8e+-yh-string is revolved at a uniform rate in a vertical cirbc/(+bke b )fjcle of radius 72.0 cm , as shown in Fig. 5-3+b( b/j cfb)ke3. If its speed is 4.00 $\mathrm{~m} / \mathrm{s}$ and its mass is 0.300 kg , calculate the tension in the string when the ball is (a) at the top of its path
(b) at the bottom of its path.
