When a body is dropped from a tower, it covers 75% of total height of the tower in the last second of its fall. What is the total height of the tower?
A
4.9 m
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B
9.8 m
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C
5.6 m
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D
6.0 m
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Solution
The correct option is B4.9 m Let h be the height of the tower the initial velocity u=0 h=12gt2Sn=g2(2t−1)=0.75h=g2(2t−1)=0.75(12gt2)(from1))2t−1=75t2100=34t28t−4=3t23t2−8t+4=0t=8±√64−4×3×42×3=8±√1612=8±412t=1,−2/3⇒t=1sh=12×gt2=12×9.8×1=4.9m