The water in the river moves with the speed 0.523 km/h. Alice and Bob can swim with the speed 2.62 km/h with respect to the water. They want to get from point A on one bank of the river to point B directly across on the other bank. Alice swims along the straight line AB, while Bob swims with a velocity perpendicular to the river and lets the flow take him some distance downstream. After that, he walks to point B along the river. What is the speed of his walk if he reaches point B at the same time as Alice

b.transmitters send radio waves, and receivers capture radio waves.

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.