A ball dropped from a balloon at rest clears a tower 81m high during the last quater second of its journey. Find the height of the balloon and the velocity of the body when it reaches the ground.WHAT IT MEANS- LAST QUATER SECOND OF ITS JOURNEY. Solution) The last quarter of the jouney menas 1/4th of the total time it requires in its total journey.Let total time be 4t, u = 0.So, v at 3t = 3gt, and at 4t = 4gt.by v² = u² + 2as,16g²t² = 9g²t² + 2g(81)7g²t² = 162g7gt2 = 162t² = 162 / 7gt = 1.5 sec.but time is 4t = 6 sec.So velocity on reaching = 4gt = 58.8 m/sWith this velocity, height of fall = 2t(58.8) = 705.6m