Question 57 of 308

A stone is dropped from the top of a building. When it crosses a point $5m$ below the top, another stone starts to fall from a point $25m$ below the top. Both stones reach the bottom of building simultaneously. The height of the building is :

A$25m$B$45m$C$35m$D$50m$

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Answer: (B) $45m$

Time for particle to meet $=t'=\dfrac{{S}_{rel}}{{S}_{rel}}=\dfrac{20}{10}=2\sec$
Time taken by ${I}^{st}$ particle to reach ground $=3\sec$
$H=\dfrac{1}{2}g{\left(3\right)}^{2}=45m$