Chapter 5, Problem 12P

GO Two horizontal forces ${\stackrel{\to }{F}}_1$ and ${\stackrel{\to }{F}}_2$ act on a 4.0 kg disk that slides over frictionless ice, on which an xy coordinate system is laid out. Force ${\stackrel{\to }{F}}_1$ is in the positive direction of the x axis and has a magnitude of 7.0 N. Force ${\stackrel{\to }{F}}_2$ has a magnitude of 9.0 N. Figure 5-32 gives the x component v_x of the velocity of the disk as a function of time t during the sliding. What is the angle between the constant directions of forces ${\stackrel{\to }{F}}_1$ and ${\stackrel{\to }{F}}_2$?

Figure 5.32 Problem 12.