弹簧秤的弹簧断了,拆去断掉的较短部分,把剩下的较长部分弹簧仍装在原来的弹簧秤上,零点校正后,用它测力,则测量结果( )

如图所示,一根弹簧一端挂在墙上,用490N的力拉另一端,弹簧伸长了20cm。如果改为两个人分别拉弹簧的两端,把它也拉长了20cm,则每个人分别用力为( )

如图所示,是一架电梯匀速向上运动的示意图.如果用F表示钢索的拉力,用G表示电梯受到的重力,那么,能正确表示电梯受到的力的示意图是( )

下列四个事例中,其中与另外三个力所产生的作用效果不同的是( )

物体从光滑的斜面滑下的过程中(不计空气阻力),受到的力有( )

The question is         that nobody can answer it.

We are not sure if it        tomorrow. If it        , our sports meeting will be put off.

In summer, food goes bad easily         it is put in the refrigerator.

—I hear Jack Chan will come to Laiwu next week.—Really?        he comes, my younger sister will be very happy.

        it's difficult to make her dream come true,she never gives up.