Answer:
0.98 [sec].
Explanation:
1) the time when the player is moving up equals the time the player falls, it can be 't'. Then
2) the equation of moving down can be written as
[tex]\frac{g*t^2}{2} =h, \ where[/tex]
g=10 [m/s²], t - time, h - the given height.
3) according to the formula above the time spent to moving down is:
[tex]t=\sqrt{\frac{2h}{g}};[/tex]
[tex]t=\sqrt{\frac{2.4}{10}}=\sqrt{0.24} =0.49[s].[/tex]
4) finally, the total time is t*2=0.98[sec].
