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CBSE Class 11-science Answered

A body dropped from the top of the tower covers a distance of 7x in the last second of its journey where x is the distance covered in first second. How much time does it take to reach the ground?
Asked by advsamarth | 29 Jun, 2019, 16:51: PM
answered-by-expert Expert Answer
WE need to use the formulas :-  S = u×t + (1/2)g×t2   and    v = u + gt
where u is initial speed, v is speed after t seconds, g is acceleration due to gravity and S is distance travelled after t seconds
 
Distance covered in first second = (1/2) g  = x ...............(1)
 
( In eqn.(1), since the body is dropped from top of tower u = 0 also t = 1 s )
 
Let the time taken by the body to hit the ground be n seconds
 
velocity after (n-1) seconds = (n-1)g ...................(2)
 
distance covered in nth second = (n-1)g+(1/2)g = 7x  ..................(3)
 
using eqn.(1) and eqn.(3), we have, (n-1)g+(1/2)g = (7/2)g  or  n = 4 seconds
Answered by Thiyagarajan K | 29 Jun, 2019, 20:32: PM

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