A ball thrown vertically upwards after reaching a maximum height h returns to the starting point aftera time of 10s. Its displacement after 5 s is

The position of an object is always expressed w.r.t. some reference point. If the initial position of an object w.r.t. a reference points is s1 and after sometime, it changes to s2, then the magnitude of the displacement of the object is s2 - s1. Since, the given ball returns to its starting point in 10s. So, in 5s, it reaches the highest point which is at s2.Given, s2 is at a height h w.r.t. s1. Thus, the displacement after 5s will be s2 - s1 = h.