[填空题]
A ball on the end of a string is revolvedyhz:b9rx1 rajl+ +) xr at a uniform ranwl;q)8 4cit zte in a vertical circle of radius 72.0 cm , as shown in Fig. 5-33. If its spez; 4t )8cqnlwied 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.
