30. A force is exerted on a box and an equal and opposite force is exerted by the box. What explains this?
a conservation of energy
b Newton's first law of motion
c Newton's second law of motion
d Newton's third law of motion

Newtons third law of motion

Explanation:

According to Newtons third law of motion: Every action has an equal and opposite reaction.

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.