题目

Carrots are easy to raise and easy to harvest. They taste good.  __1__ When people think of carrots，they usually picture in their mind a vegetable that is long，thin and orange. __2__ And not all carrots are orange. For example，Paris Market carrots are about five centimeters around.  Rome carrots are thin and about twenty­five centimeters long. And Belgian carrots are，as their name suggests，white. For the best results，carrots should be grown in sandy soil that does not hold water for a long time. The soil also should have no rocks. To prepare your garden for carrots，di如图所示，ABC是光滑轨道，其中AB是水平的，BC是与AB相切的位于竖直平面内的半圆轨道，半径R=0.4m。质量m=0.5kg的小球以一定的速度从水平轨道冲向半圆轨道，经最高点C水平飞出，落在AB轨道上，落点距B点的水平距离s=1.6m。g取10m/s2，求： （1）小球经过C点时的速度大小；（2）小球到达半圆轨道起点B之前，轨道对小球的支持力和刚通过时轨道对小球的支持力的比值（）。