a person throws a baseball into the air with an initial vertical velocity of 30 feet per second and then lets the ball hit the ground. The ball is released 5 feet above the ground. How long is the ball in the air?

Answer 1

hf=ho+vi*t-g/2 * t^2
0=5+30t-4.9t^2
solve the quadratic with the quadratic equation.

Answer 2

h=-16t^2 + Vot + h (equation)
5=-16t^2 + 30t + 5
subtract 5
0 = -16t^2 + 30t
factor out a t
0=t (-16t + 30)
0=t 0r -16t + 30=0
13 / 16
approximately 1.87 second