A healthy young man standing at a distance of

For kid,

$\mathrm{u}=0 ; \mathrm{a}=\mathrm{g} ; \mathrm{s}=11.8-1.8$

$\mathrm{s}=10 \mathrm{~m}$

$s=u t+\frac{1}{2} a t^{2}$

$10=0+\frac{1}{2}(g) t^{2}$

$t=1.42 \mathrm{sec}$

In this time, man has to reach building

Speed= $\frac{\text { distance }}{\text { time }}=\frac{7}{1.42}$

$=4.9 \mathrm{~m} / \mathrm{s}$