Answer:
2.54 seconds
Step-by-step explanation:
We can use the following equation to model the vertical position of the ball:
S = So + Vo*t + a*t^2/2
Where S is the final position, So is the inicial position, Vo is the inicial speed, a is the acceleration and t is the time.
Then, using S = 2.5, So = 0.4, Vo = 14 and a = -9.8 m/s2, we have that:
2.5 = 0.4 + 14*t - 4.9t^2
4.9t^2 - 14t + 2.1 = 0
Solving this quadratic equation, we have that t1 = 2.6983 s and t2 = 0.1588 s.
Between these times, the ball will be higher than 2.5 m, so the amount of time the ball will be higher than 2.5 m is:
t1 - t2 = 2.6983 - 0.1588 = 2.54 seconds
