### Home > APCALC > Chapter 5 > Lesson 5.1.3 > Problem5-29

5-29.

Kwok is standing on top of a $160$-foot tall building and throws a tennis ball straight up with an initial velocity of $24$ ft/sec.

$h\left(t\right) = −16t^{2} + v_{0}t + s_{0}$

1. How far up does the tennis ball go before it turns around and starts to come down?

The tennis ball turns around when $v\left(t\right) = 0$.

2. How fast is it going when it hits the ground below?

Evaluate $v\left(\text{time of impact}\right)$. Let $h\left(t\right) = 0$ to find the time of impact.