问题
听力题
单词拼写(共5小题; 每小题1分, 满分5分)
根据首字母或汉语提示，在句子中填入适当的单词。
小题1:Bamboo grows up straight and thin, with b____ at the top.
小题2: He had attempted to rescue the _____（溺水的）man.
小题3:The i_____ of the computer marked the beginning of a new era.
小题4:A red light is usually a _____ (信号) of danger.
小题5:John is _____ (订婚) to Mary.
答案
branches drowning invention signal engaged
，在斜面底端有一与斜面垂直的绝缘弹性挡板。质量m=0.2kg的带电滑块从斜面顶端由静止开始下滑，滑到斜面底端与挡板相碰撞后以碰前的速率返回。已知斜面的高度h=0.24m，滑块与斜面间的动摩擦因数u=0.30，滑块带电量q=-5×
.重力加速度g=10
，sin37°=0.60，cos37°=0.80.求：