Question

A stone falls from the top of a building and travels 53.9m in the last second before it reaches the ground. Find the height of the building

Answer 1

Hope it might help you

Answer 2

We know, distance travelled in a second

$S_{n}=u+\frac{a}{2}(2n-1)\\\Rightarrow 53.9=\frac{9.8}{2}(2n-1)\\\Rightarrow n=6$

Since $n=6$that means the last second is the 6th second, the stone travelled for 6s.

Now, $S=ut+\frac{1}{2}gt^{2}\\\Rightarrow=0+\frac{1}{2}{9.8}{6}^{2}=176.4 m$

The height of the building is 176.4 m

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