\[1)\ 120 = V_{0} \cdot 2 - 5 \cdot 2²\]
\[120 = V_{0} \cdot 2 - 20\]
\[2V_{0} = 140\]
\[V_{0} = 70\ \frac{м}{с}.\]
\[2)\ 240 = 70t - 5t²\]
\[5t² - 70t + 240 = 0\ \ \ |\ :5\]
\[t^{2} - 14t + 48 = 0\]
\[D = b^{2} - 4ac =\]
\[= 196 - 4 \cdot 1 \cdot 48 =\]
\[= 196 - 192 = 4\]
\[t_{1} = \frac{14 + 2}{2} = \frac{16}{2} = 8\]
\[t_{2} = \frac{14 - 2}{2} = \frac{12}{2} = 6\]
\[Ответ:тело\ окажется\ \]
\[на\ высоте\ 240\ м\ в\ 6\ с\ и\ 8\ с.\]