Question

47. A stone dropped from the roof of a building
takes 4 s to reach the ground. The height of the
building is
(a) 9.8 m
(b) 19.6 m
(c) 39.2 m
(d) 78.4 m

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Answer 1

Answer:

you are right answer is a 9.8 so please please please make me brainliest

Answer 2

Answer:

(d) 78.4m

Explanation:

The acceleration of the stone is g (9.8m/s²)

s = ut + at²/2

where 's' is the distance covered by the stone(the height of the building) .

'u' is the initial velocity of the stone, which is 0.

't' is the time taken by the stone.

'a' is the stone's acceleration.

So, s = 0(4) + 9.8(4²)/2 = 9.8(8)

= 78.4m