Chapter 2.3, Problem 107E

Free-Falling Object In Exercises 107 and 108, use the position function $s\left(t\right)=-4.9t^2+200$, which gives the height (in meters) of an object that has fallen for t seconds from a height of 200 meters. The velocity at time $t=a$ seconds is given by

$\underset{t\to a}{\lim }\frac{s\left(a\right)-s\left(t\right)}{a-t}\cdot$

Find the velocity of the object when $t=3$.