\( OY: S=S_{1} - S_{0} \ S_{1} = \frac{gt^2}{2} \ S_{0} = \frac{g(t-1)^2}{2} \)
\( \frac{gt^2}{2} - \frac{g(t-1)^2}{2} = 35 \ 2gt-g=35 \ t= \frac{70+g}{2g} =80/20=4 \) (с
Ответ: 4 c.