Question

If a baseball player hits a baseball from 4 feet off the ground with an initial velocity of 64 feet per second, how long will it take the baseball to hit the ground? Use the equation h = −16t2 + 64t + 4.

Answer 1

You need to find the roots of the function, h(t)

then h(t) = 0 = -16t^2 + 64t + 4

divide both sides by -4

4t^2 - 16 t - 1 = 0

use the quadratic function

$\frac{-b+/- \sqrt{b^2-4ac} }{2a}$

substitue a = 4, b = -16, c = -1

you will get t1 ≈ 0 and t2 ≈ 4

Answer: approx. 4 seconds.