A stone is dropped from the top of a building. When it crosses a...

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 stone is dropped from the top of a building. When it crosses a point 5m below the top, another stone starts to fall

A stone is dropped from the top of a building. When it crosses a point 5m below the top, another stone starts to fall

Options

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

Correct answer

B. $45m$

Step-by-step solution

A stone is dropped from the top of a building. When it crosses a point 5m below the top, another stone starts to fall

Time for particle to meet $= t ' = \dfrac{{S}_{rel}}{{S}_{rel}} = \dfrac{20}{10} = 2sec$

Time taken by ${I}^{st}$ particle to reach ground $= 3sec$

$H = \dfrac{1}{2}g{\left(3\right)}^{2} = 45m$

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