Correct Answer: Option A

Explanation

Using the equation

S = ut + ½ gt²

H = s = 20m, t = ?

G =10m/s², u = 0m/s

20 = 0 × t × ½ × 10 t

20 = 5t

i.e 5t² = 20

t = 20/5 = 4

t = 4 (squaring both sides)

√ t² = √4

= 2sec

∴ t = 2sec

There is an explanation video available below.

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