A roller coaster car picks up speed as it rolls down the slope. As it starts down the slope, its speed is 4 m/s. It accelerates at a rate of 6 m/s/s. What is its
velocity after 3 seconds? *

22 m/s

Explanation:

v(t) = Vo + at

v(3) = 4 + 6*3

v = 4 + 18

v = 22 m/s (almost 50 miles/hour)

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.