### Home > PC > Chapter 11 > Lesson 11.1.2 > Problem 11-31

11-31.

A water balloon is tossed from the top of a walkway so that its height above the ground is found by *h*(*t*) = −16*t*^{2} + 20*t* + 50 where *h* is measured in feet and *t* is measured in seconds. Approximate the instantaneous velocity of the water balloon when it strikes the ground. Homework Help ✎

First determine when the ball hits the ground, or when *h*(*t*) = 0.

The ball hits the ground when *t* = 2.5 seconds.

The velocity is the instantaneous rate of change (IROC). See the Math Notes box in Lesson 9.2.1 for the formula.