题目

（湖南省长沙市一中2010届高三第九次月考A篇） After so much discussion — featured by intense media attention and China's repeated warnings — US President Barack Obama finally met the Dalai Lama at the White House on Thursday. With this latest move to test China's limit of tolerance, Obama has hit a home run to complete his months-long season of a game called antagonizing (敌对的) China. At least we hope so. After all the recent tensions in Sino-US relations, a half-time break is what both sides desperately need. But it is still too early to have a sigh of relief重50N的物体在10N水平拉力的作用下沿水平方向匀速运动了5m，则拉力做的功是______J．