题目

阅读理解 Chocolate is good for your heart, skin and brain. Usually, people thinkthat chocolate is bad for their health. They describe chocolate as somethingto die for or say death by chocolate. Now they should bite their tongues! Evidence(证据)is showing that some kinds ofchocolate are actually good for you in the following ways: A happier heart. Scientists at Harvard University recently examined 136 studies oncocoa—the main ingredient(成分)in chocolate and found that it does seem to strengthen the heart. Better blood pressure. Jeffrey Blumberg from Tufts University recently foun（2007?惠州模拟）如图所示，质量均为m的A．B两球间有压缩的短弹簧，弹簧处于锁定状态，若整个装置放置在水平面上竖起．光滑的发射管内（两球的大小尺寸和弹簧尺寸都可忽略，它们整个可视为质点），解除锁定后，A球能上升的最大高度为H，现在让两球包括锁定的弹簧从水平面出发，沿光滑的半径为R的半圆槽从右侧由静止开始下滑，至最低点时，瞬间锁定解除，求A球离开圆槽后能上升的最大高度．