题目

Will you please tell us _______ before you came to our City?  A．where do you work                        B．where did you work   C．where you worked                         D．where you are working 答案：C11．如图所示，在悬点O处用长为L的细绳拉着质量为m的小球，在半径为R的光滑半球面上静止．已知悬点离半球面的竖直高度为h，试求①半球对小球的支持力和细绳对小球的拉力；②小球向上运动过程中支持力及拉力的变化情况．