B) A stone is dropped from the roof of a four storey building. The height of each storey is 4.9m . Taking g =9.8m/s2 , calculate the velocity with
which the stone will hit the ground.

9.8m/s

Explanation:

Given,

distance of each storey () = 4.9m

distance of 4 storey (s) = 19.6m

acceleration due to gravity (g) = 9.8 m/s^2

time given (t) = ?

velocity = (?)

initial velocity (u) = 0 {due to fall from certain height}

using formula,

s = ut + 1÷2at^2

s = 0 + 9.8÷2×t^2

19.6×2÷9.8 = t^2

4 = t^2

t = 2

now,

velocity ( v )= s ÷ t

v = 19.6 ÷ 2

v = 9.8 m/s

ans

it is a negative acceleration

total distance/total time

(85 + 82)/(5+3)

167/8

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