阅读下面短文，在空白的地方填入适当的内容（不多于三个单词）或括号内单词的正形式
It was the ambition of an eleven year old boy in Kansas City to be an engine-driver. Born without arms, he had been sent to special schools he learned to use his
(foot) as “ hands”. He spent all his spare time
(watch) trains and one day his dream came
(true). Seeing a deserted engine , the boy climbed in, he had no
(difficult) in starting it up with his feet . Soon he was traveling along
forty miles an hour. Signalmen could not see the young driver, so they set out
(stop) the train. Meanwhile the boy reached Missouri, stopped the engine himself, and then made it
(go) backwards. When he was near home, a railway-man caught up with the engine and stopped it. At first, he was very angry, but he smiled
the boy said simply, “I like trains.” “Well, I’m glad you don’t like planes!” answered
railway-man.
如图所示是一款“运动手环”，其主要部分是一段内置一小块磁铁的密闭空心塑料管，管外缠绕着线圈。戴着这种手环走路时，塑料管跟着手一起运动，磁铁则在管内反复运动，线圈中便会产生电流，液晶屏上就会显示出运动的步数，此过程利用了 的原理，将 能转化为电能。
在弹簧测力计下挂一个圆柱体 ，让 从盛有水的容器上方逐渐竖直浸入水中，弹簧测力计的示数随圆柱体下表面在水中深度的变化关系如图，则圆柱体 的底面积为 ，取
如图，电源电压为 且保持不变，闭合 时，电压表的示数为 ，电流表的示数为 ，则 ， 、 消耗的电功率之比为 。
一个空心小铁球放在盛水的烧杯中置于铁棒 的上方，绕在铁棒上的线圈连接如图所示的电路，开关 闭合后，空心小铁球仍漂浮在水面上，此时 端为电磁铁的 极，当滑片 向左滑动，空心小铁球所受浮力 （选填“增大”、“减小”或“不变”
如图，有一圆柱形容器，放在水平桌面上。现将一体积为 ，质量为 的矩形金属块放在容器底部，再向容器中加入水至 深时，水对容器底的压强是 ，金属块对容器底部的压力是 （金属块与容器底部不是紧密接触， ，取 。
