词语运用
①The old man is d____.He can't hear anything.
②My dog is m____.Can you help me find it?
③All of them are ____(注视) at the computer screen.
④We don't know whether he's ____(活着)or dead.
⑤The road was so narrow(狭窄)that cars were unable to ____(通过).
一质量为m的木块静止在光滑的水平面上,从t=0时刻开始,将一个大小为F的水平恒力作用在该木块上,在t=t1时刻F的功率和时间t1内的平均功率分别为( )
辨析:唯物主义都是科学的,因而都是我们应该提倡的。
小刚同学为探究环境条件对菜豆种子萌发的影响,设计了如表所示实验,10天后,甲组种子萌发,乙组种子未萌发,乙组种子未萌发的主要原因是( )
甲组
25℃
无光照
适量的水
乙组
水淹没种子
关于光现象,下列说法正确的是( )