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Grade 10General Physics

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.

Profile image of ADITYA PRAKASH
13 Years agoGrade 10
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2 Answers

Profile image of Manas Satish Bedmutha
13 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

Pleases approve this!!!

Profile image of Nitesh roshan
7 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