일반물리학 1 — Motion Along a Straight Line: Problem 56

56 Figure 2-21 shows the speed v versus height y of a ball tossed directly upward, along a y axis. Distance d is 0.40 m. The speed at height \(y_A\) is \(v_A\). The speed at height \(y_B\) is \(\frac{1}{3}v_A\). What is speed \(v_A\)?