\(S_2\) in first \(p\) sec
\( \mathrm{S}_1=\frac{1}{2} \mathrm{a}(\mathrm{p}-1)^2 \)
\( \mathrm{~S}_2=\frac{1}{2} \mathrm{a}(\mathrm{p})^2 \)
\( \mathrm{~S}_1+\mathrm{S}_2=\frac{1}{2} \mathrm{at}^2 \)
\( (\mathrm{p}-1)^2+\mathrm{p}^2=\mathrm{t}^2 \)
\( \mathrm{t}=\sqrt{2 \mathrm{p}^2+1-2 \mathrm{p}}\)
($g = 9.8\,m/{s^2}$)