题目

Look at these pictures carefully, and decide which sentence is right.      A. Coke is as cheap as orange juice.   B. Milk is cheaper than orange juice.   C .Orange juice is not so cheap as coke. 答案：C11．一细杆与水桶相连，水桶中装有水，水桶与细杆一起在竖直平面内做圆周运动，如图所示，水的质量m=0.5kg，水的重心到转轴的距离l=50cm．（1）若在最高点水不流出来，求桶的最小速率；（2）若在最高点水桶的速率v=3m/s，求水对桶底的压力．