If two parallel light rays hit a plane mirror, what will be their orientation to one another after they reflect?
a. they will remain parallel.
b. they will be perpendicular.
c. it depends on the initial spacing between the light rays.
d. it depends on the angle at which they strike the mirror.

trig 15.3 cos

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.