题目

如图所示，光滑水平面AB与竖直面内的半圆形导轨在B点衔接，导轨半径为R，一个质量为m的小球将弹簧压缩至A处。小球从A处由静止释放被弹开后，经过B点进入导轨瞬间对导轨的压力为其重力的8倍，之后向上运动恰能沿轨道运动到G点，求： （1） 释放小球前弹簧的弹性势能。 （2） 小球由B到C克服阻力做的功。First, collect as many stamps as you can. Second, trade ________ you don’t want to keep with other people. A．whatever B．no matter with C．however D．whichever