gt1^2/2=h1

 t1=sqrt(2h1/g)=sqrt(20)

t2=sqrt(18)

t=4,4-4.24=0.16 pervye desyat metrov

100 metrov =10raz po 10 metrov

16-0,16=15,84 sec 

\( h=v_{0}+\frac{at^{2}}{2} \)
\( v_{0}=0 \)
Выразим \( t_{0}=\sqrt{\frac{2h}{g}} \)
\( t_{100}=t_{90}+t_{10} \), получаем: \( t_{90}=t_{100}-t_{10} \)
\( t_{90}=\sqrt{\frac{2*100}{10}}-\sqrt{\frac{2*90}{10}}=0.2 \)
\( t_{10}=\sqrt{\frac{2*10}{10}}=1.41 \)