Why is it better system for units?

Because it's so much simpler and easier to use. The metric system is an improvement over the English system in three major points: One unit of measurement for each physical quantity. No matter from which other quantities of the SI system derived, yields always the same unit.

Explanation:

1 a

2 b

3 b

4 d

5 d

6 d

explanation:

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.