Question

How long will it take an object dropped from a window to fall a distance of 78.4 meters?

Answer 1

As you said it was dropped so in that case I'll take 78.4 meters as the height..
we know that
h = ut + 0.5*g*t(sqr)
t(sqr) = 78.4/(0.5*9.8) [g = 9.8 ms-2]
t = √16
t = 4
So it'd take 4 seconds

Answer 2

Answer:

The time is 4 sec.

Step-by-step explanation:

Given that,

Distance = 78.4 m

We need to calculate the time

Using equation of motion

$s=ut+\dfrac{1}{2}gt^2$

$t =\sqrt{\dfrac{2s}{g}}$

Where, s = distance

g = acceleration due to gravity

t = time

$t =\sqrt{\dfrac{2\times78.4}{9.8}}$

$t=4\ sec$

Hence, The time is 4 sec.