### Home > APCALC > Chapter 2 > Lesson 2.3.2 > Problem 2-119

When the balloon in problem 2-81 reached , where

*is the number of seconds since the time it popped and*

*is the height of the balloon (in feet) above the ground.*

According to the model, when will the balloon hit the ground?

What value of

represents the ground?Approximate the balloon’s velocity at

seconds.Velocity is slope of a distance/position graph. Since

is a parabola, we do not have the skills (yet) to find the slope on a curve. But we can approximate. Choose two times very close to

. Use the function,, to find the balloon's height at those times. Find the slope of the line that goes through those points. This will be a good approximation of the velocity of the balloon at .