题目

A little girl lived in a simple and poor house on a hill．Usually she （16）    play in the small garden．She could see over the garden fence and across the valley a wonderful house with shining golden windows high on another hill．（17）      she loved her parents and her family，she desired to live in such a house and  （18）          all day about how wonderful and exciting   （19）  must feel to live there． At the age when she gained some  （20）      skill and sensibility（识别力），she （21）  her mother for a bike ride （22） �质量m=1000kg的汽车通过圆形拱形桥时的速率恒定，拱形桥的半径R=5m．试求：（1）汽车在最高点对拱形桥的压力为车重的一半时汽车的速度；（2）汽车在最高点对拱形桥的压力为零时汽车的速度．（重力加速度g取10m/s2）