In the last second of free fall, a body covered 34th of its total path. Then the height from which the body is released will be g=10 m/s2
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a
10m
b
20m
c
30m
d
40m
answer is B.
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Detailed Solution
If ‘n’ is the last second, then the distance travelled by a freely falling body in ‘n’ sec iss=12gt2 (∵u=0)=12gn2……..(1) and sn=gn−12……...(2) Given that sn=34s⇒gn−12=3412gn2∴(2n−1)=34n2⇒(2n−1)n2=34⇒n=2sThe height from which the body is released is s=12gn2 =12×10×(2)2=20m