Answer:
c. 0.71 [s]
Step-by-step explanation:
To solve this problem we must use the following equation of kinematics.
![v_(f) =v_(o) -g*t](https://img.qammunity.org/2021/formulas/physics/high-school/ymyzup2b8b6hwujqhs1p201jwqajmswmeb.png)
where:
Vf = final velocity = 0 (because when the ball reaches the top, there is no movement)
Vo = initial velocity = 7 [m/s]
g = gravity acceleration = 9.81 [m/s²]
t = time [s]
Note: The negative sign of the equation means that the movement is againts the direction of the gravity acceleration.
![0 = 7 - (9.81*t)\\t = 0.713 [s]](https://img.qammunity.org/2021/formulas/physics/high-school/xjldwx1dicu1fenky33ncvpmpuzgzw46mv.png)