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# 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.

Manas Satish Bedmutha
22 Points
8 years ago

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 = 162g

7gt2 = 162

t² = 162 / 7g

t = 1.5 sec.

but time is 4t = 6 sec.

So velocity on reaching = 4gt = 58.8 m/s

With this velocity, height of fall = 2t(58.8) = 705.6m

Nitesh roshan
15 Points
2 years ago
2648.2m,324.38m/s
( Hope this answers.might help you ) upper person who have given the ans. Is written wrong
. But my ans. Is correct