吊车以2m/s的速度将重物1×105N匀速向上提起，这时钢索对重物的拉力是____N； 若钢索改为以3m/s的速度使重物匀速下降，此时钢索对重物的拉力大小是____N，方向____.
As you go through this book, you ________ that each of the millions of people who lived through World War II had a different experience.
根据下列实验方案进行实验，能达到相应实验目的是（ ）
