The uniform 12-kg slender rod is pinned to a small roller a that slides freely along the slot. if the rod is released from rest at θ = 0°, determine the angular acceleration of the rod, the acceleration of the rod’s center of mass and the acceleration of the roller immediately after the release.

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.

beta is electron from nucleus

something from nucleus has changed, but charge must be same for cons of charge