40. CHALLENGE You stack two physics books on top of each other as shown in Figure 19. You tilt the bottom book until the top book just begins to slide. You perform five trials and measure the angles given in Table 3.
a. What is the average ∅ measured during the five trials?
b. What is the coefficient of static friction between the covers of the two books? Use the average ∅ found in part a.
c. You measure the top book's acceleration down the incline to be 1.3m/s². What is the coefficient of kinetic friction? Assume ∅ is the average value found in part a.