How long does a ball take to fall from a roof to the ground 7 m below?

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How long does a ball take to fall from a roof to the ground 7 m below?

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Answer 1 · 2018-05-07T09:07:33

See below

Explanation:

If we assume that there is no air resistance and the only force acting on the ball is that of gravity, we can use the equation of motion:

$s = u t + (\frac{1}{2}) a t^{2}$ $s=ut+(1/2)at^(2)$

$s$ $s$ =distance travelled
$u$ $u$ =initial velocity (0)
$t$ $t$ =time to travel given distance
$a$ $a$ =acceleration, in this case $a = g$ $a=g$ ,the acceleration of free fall which is $9.81 m s^{- 2}$ $9.81 ms^-2$

Hence:
$7 = 0 t + (\frac{1}{2}) 9.81 t^{2}$ $7=0t + (1/2)9.81t^2$

$7 = 0 + 4.905 t^{2}$ $7=0+4.905t^2$

$\frac{7}{4.905} = t^{2}$ $7/(4.905)=t^2$

$t \approx 1.195 s$ $t approx 1.195 s$

So it takes barely a second for the ball to hit the ground from that height.

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How long does a ball take to fall from a roof to the ground 7 m below?

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