如图甲所示,重量为4N的正方体铁块,被水平吸引力吸附在足够大的竖直磁性平板上处于静止状态,这时铁块受到的摩擦力大小为________N;若对铁块施加一个竖直向上的拉力F=9N的作用,铁块将沿着该平板匀速向上运动,如图乙所示,此时铁块受到的摩擦力大小为________N.
根据提供的图画和提示词,写一个符合图意的完整、正确的句子.
collect,fun .
face,now .
It was a difficult time for them,but they didn't give up (放弃)their hope.
﹣We'd better book a standard room before we set off.
﹣I (同意)with you.
Telescopes are (有用的).We can look at the universe through them.