题目

 If you woke up this Monday feeling depressed and found that, from then on, things got worse, there may be an explanation. According to one psychologist’s (心理学家) calculations, January 23 was the most depressing day of the year for the British. Cliff Arnall, a psychologist at Cardiff University who worked out the formula (公式), blamed a combination of debts, failed New Year’s plans, the cold, grey weather and the length of time since Christmas. “For most people, there’s a realization by the third week of January that spending on sales items needs to be stopped so t小明在“测滑轮组机械效率”的实验中，用如图甲所示的滑轮组进行实验，实验数据如下表．实验序号物重G/N物体上升的高度h/m测力计的示数F/N测力计移动的距离s/cm机械效率η1250.91574.1%22100.93074.1%34101.73078.4%46102.530 （1）分析表中数据，可知滑轮组的机械效率与物体上升的高度______，与所提物体的重力大小______；（均选填“有关”或“无关”）（2）请用实验中所测量的量算出第4次实验的机械效率为______；（3）如果换用图乙所示装置进行实验，把同一重物提升相同高度，需要做的额外功更______，所以机械效率更______；（均选填“大”或“小”）（4）关于用同一滑轮组提升重物时的机械效率，以下说法正确的是______A．提升越重的物体，机械效率越大    B．功率越大，机械效率一定越大C．额外功越大，机械效率一定越小    D．同一机械的机械效率是恒定不变的（5）在正确操作该实验时，应该沿着竖直方向匀速拉动弹簧测力计，若某同学在实验时加速拉动弹簧测力计，则所测得的滑轮组机械效率与正确操作实验相比将______（选填“偏大”、“不变”或“偏小”）