Answer:
2.1 s
Step-by-step explanation:
The motion of the ball is a projectile motion. We know that the horizontal range of the ball is
![d = 50 m](https://img.qammunity.org/2020/formulas/physics/high-school/ef8yb13u6wl3u9619d2qqvxax36qjbbxeh.png)
And that the initial speed of the ball is
![u=25 m/s](https://img.qammunity.org/2020/formulas/physics/high-school/c32crhe27y2d22r99smyyoqf2bedsn18mr.png)
at an angle of
![\theta=20^(\circ)](https://img.qammunity.org/2020/formulas/physics/college/2l72u5k89kkwwpets8tlswsu2e5j2p3zq5.png)
So, the horizontal speed of the ball (which is constant during the entire motion) is
![u_x = u cos \theta = 25 \cdot cos 20^(\circ) = 23.5 m/s](https://img.qammunity.org/2020/formulas/physics/high-school/ey3h6u8gqcwddyat8wjs7srvlwb33ff824.png)
And since the horizontal range is 50 m, the time taken for the ball to cover this distance was
![t=(d)/(u_x)=(50)/(23.5)=2.1 s](https://img.qammunity.org/2020/formulas/physics/high-school/q1ckjvkolutflukb7nefp6y0wigazean96.png)
which is the time the ball spent in air.