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Physics

A body falls from the top of a building and reaches the ground 2.5 s later. How high is the building ? (Take g = 9.8 m s-2)

Laws of Motion

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Answer

From the equation of motion,

h = ut + 12\dfrac{1}{2} gt2

Given,

g = 9.8 m s-2

t = 2.5 s

u = 0

Substituting the values in the formula, we get,

h=(0×2.5)+(12×9.8×2.52)h=0+(4.9×2.52)h=4.9×(2.5)2h=30.6mh = (0 \times 2.5) + (\dfrac{1}{2} \times 9.8 \times 2.5^2) \\[0.5em] h = 0 + (4.9 \times 2.5^2) \\[0.5em] h = 4.9 \times (2.5)^2 \\[0.5em] h = 30.6 m \\[0.5em]

Hence, the height of the building is 30.6 m

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