A stone is dropped from a height of 20 m. How long will it take to reach the ground? ( $g = 10 m / s^{2}$ ).

2 s

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0.5 s

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4 s

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1 s

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Solution

The correct option is A 2 s
Given,
$u = 0 m / s$
$g = 10 m / s^{2}$
$h = 20 m$

3rd equation of motion,
$2 g h = v^{2} - u^{2}$
$2 \times 10 \times 20 = v^{2} - 0^{2}$
$v^{2} = 400$
$v = 20 m / s$

1st equation of motion,
$v = u + g t$
$20 = 0 + 10 t$
$t = \frac{20}{10} = 2 s e c$
The correct option is A.

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A stone is dropped from a height of 20 m. How long will it take to reach the ground? (g=10m/s2 ).

The correct option is A 2 sGiven,u=0m/sg=10m/s2h=20m3rd equation of motion,2gh=v2−u22×10×20=v2−02v2=400v=20m/s1st equation of motion,v=u+gt20=0+10tt=2010=2secThe correct option is A.

A stone is dropped from a height of 20 m. How long will it take to reach the ground? ( $g = 10 m / s^{2}$ ).