If a freely falling body travels in the last second, a distance equal to the distance travelled by it in the first three second, the time of the travel is

Options

A. 6sec
B. 5sec
C. 4sec
D. 3sec

Answer

B

Explanation

Distance travel in last second
S_("lost") = g/2 (2n -1) = (9.8) (2n - 1)`
Distance travel in 1st three second
`S = 1/2 xx 9.8 xx (3)^2`
`(9.8)/(2) (2n - 1) =1/2 xx 9.8 xx (3)^2`
`rArr n = 5`