Homework VI. Ch. 7 - Problems 15, 19, 22, 25, 35, 43, 51. Problem 15. (a) The centripetal acceleration of a point on the equator of the Earth is given by v2 r . The velocity of the earth can be found by taking the ratio of the circumference of the earth to its rotational period. Thus, we find: v = 2?r. T. = 2?(6373 km). 24h(3600 s h. ).