Question

17. A particle at rest, falls under gravity (g = 9.8 m/s
such that it travels 53.9 m in last second of
journey. Total time of fall is
(1) 4s
(2) 5s
(3) 6s
(4) 7s​

Answer 1

Answer:

3) 6 s

Explanation:

Let "h" be height travelled in last second, "n" be total time and "u" be initial velocity. Then,

h = u + g/2(2n-1)

53.9 = 9.8/2 (2n-1)

53.9 = 4.9 (2n-1)

53.9/4.9 = 2n-1

11 = 2n-1

2n-1 = 11

2n = 11+1

2n = 12

n = 12/2

n = 6 sec

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Answer 2

Answer:

Total time of fall is 7 second.

Explanation: