Halliday, Resnick & Walker — Force and Motion–I: Problem 24

There are two horizontal forces on the 2.0 kg box in the overhead view of Fig. 5.21 but only one (of magnitude \(F_1 = 20\text{ N}\)) is shown. The box moves along the x axis. For each of the following values for the acceleration \(a_x\) of the box, find the second force in unit-vector notation: (a) \(10\text{ m/s}^2\), (b) \(20\text{ m/s}^2\), (c) \(0\), (d) \(-10\text{ m/s}^2\), and (e) \(-20\text{ m/s}^2\).