一个小孩推一辆车,车没动.那么摩擦力和推力二力平衡我能理解,但是推力是可以变化的,我觉得推力在一定范围内车都不会动,那么

一个小孩推一辆车,车没动.那么摩擦力和推力二力平衡我能理解,但是推力是可以变化的,我觉得推力在一定范围内车都不会动,那么摩擦力在推力变化的情况下还与推力二力平衡,就是摩擦力等于推力,但是摩擦力在压力不变、接触面表面粗糙程度不变的情况下是不变的啊、感觉好矛盾哪.-
英语1.The things he()help with her problem.
A could to do B could do C do to D did were to
2.Do you know the men who ()strong?
Yes.they are all the members of our team.
A is B looks Cwill be Dlook
这是定语从句吧?请解释清楚主句和从句的关系、从句和宾语从句一样用陈述句句式么?
3.When you burned yourself,you should put the()area under cold ()water at once.
A burning ;ran B burning;running C burned;ran D burned;running
- -请认真回答,抓住重点,不太懂的不要说啦