Answer:
t = 8.5 s
Explanation:
Kinematic equation of the movement of the tennis ball that is thrown upwards :
y = y₀ + v₀*t -½ g*t² Equation (1)
Where :
y : position of the ball as a function of time
y₀ : Initial position of the ball
t: time
g: acceleration due to gravity in m/s²
Known data
g = 32 ft/s²
y₀ = 680 ft
v₀ = 56 ft/s
Calculation of the time it takes for the ball to thit the ground
We replace data en the equation (1)
y = y₀ + v₀*t -½ g*t²
0 = 680+(56)*t -½( 32) *t²
16*t²-(56)*t- 680 = 0 equation (2)
solving equation (2) quadratic:
t₁ = 8.5 s
t₁ = -5 s
Time cannot be negative so the time it takes for the ball to hit the ground is t = 8.5 s
