A positive point charge is placed at 5 cm from a negatively charged plate. it is then pulled away from the plate, so it is 10 cm from the plate. Describe
what happened to the potential energy of the charge. (Hint what
happened to the force on the charge more force means more potential
energy)

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.

i think it's 35 meters