iv) Time of flight (tf):
"For a body projected vertically upwards the sum of time of ascent and time of descent is called time of flight (tf)" It is the total time for which the body remains in air
Time of flight = Time of ascent + Time of descent
tf = ta +td
\(
\begin{gathered}
\therefore t_f = \frac{u}
{g} + \frac{u}
{g} = \frac{{2u}}
{g} \hfill \\
\therefore t_f = \frac{{2u}}
{g} \hfill \\
\end{gathered}
\)