题目

In the past few years, quite a number of men and women have chosen to do something less competitive. They are afraid that the stress and strains of work will rob them __1___ _____ joy and happiness and __2  ______ them harm both physically and mentally.      In fact, however, stress isn’t the bad thing __3________ it is often supposed to be. Above all, __4______ it gets out of control, a certain amount of stress is vital to provide motivation and challenge, and to give purpose and significance to _5_______, otherwise meaningless, idle life. __6__________, people under stress tend to exp17．如图所示为一升降机由静止开始下降过程中的速度图象，升降机及其载重总质量为2.0t．（1）由图象判断出升降机在哪段时间内出现超重、失重现象；（2）分别求出第2S内、第5S内、第7S内悬挂升降机的钢索的拉力大小．（g取10m/s2）