What does si stand for when referring to a system of measurement

The International System of Units (SI, abbreviated from the French Système international (d'unités)) is the modern form of the metric system, and is the most widely used system of measurement.

Système international (d'unités)

Explanation:

The full form of SI is Système international (d'unités). It started around the 18th century. It is known as the International System of Units in English. The basic units of the SI system are second, kilogram, Ampere, Kelvin, mole and candela. All other units are obtained by the combination of these units. The SI system of units are used in almost all the countries of the world.

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.