Hallo, \(\displaystyle t=\sqrt{\frac h5}\) ist nicht ganz korrekt. Allgemein gilt \(\displaystyle t=\sqrt{\frac{2h}g}=\sqrt{\frac{2h}{10\dfrac m{s^2}}}=\sqrt{\frac{h}{5\dfrac m{s^2}}}\).
\(\displaystyle a)\ t_1=\sqrt{\frac{10m}{5\dfrac m{s^2}}}=\sqrt2s\)
\(\displaystyle t_2=\sqrt{\frac{20}5}s=2s\)
\(\displaystyle t_3=\sqrt{\frac{50}5}s=\sqrt{10}s\)
\(\displaystyle b)\ h=5\frac m{s^2}\cdot t^2\)
\(\displaystyle c)\ h_1=5\frac m{s^2}\cdot1^2s^2=5m\)
\(\displaystyle h_2=5\cdot2^2m=20m\)
\(\displaystyle h_3=5\cdot5^2m=125m\)