Two charged small spheres are a distance r apart and exert an electrostatic force f on each other. if the distance is halved to r/5 , the force exerted on each sphere will be..
a) 25f
b) 5f
c) f/5
d) f/25

a) 25F

Explanation:

Assuming that the two small spheres can be modeled as point charges, according to Coulomb's law, the magnitude of the electrostatic force is given by:

In this case, we have :

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.