Answer:
c. 0.71 [s]
Explanation:
To solve this problem we must use the following equation of kinematics.
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.