## Fundamentals of Physics Extended (10th Edition)

The box is 2kg. We are shown F1 is acting towards the right along the x axis and that it has a magnitude of 20N. In part a, we are told that ax = 0$m/s^2$. Since F = ma then the Force = 2kg * 0 $m/s^2$ = 0N. Since F1 is already 20N, then F2 must be -20N because F1 + F2 = 0N