Chapter 2 - Differentiation - 2.2 Exercises - Page 116: 99

$5$ seconds later, $71$ meters per second. $10$ seconds later, $22$ meters per second.

$s(t)=-4.9t^2+v_0t+s_0$ $\frac{d}{dx}s(t)=v$ $\frac{d}{dx}s(t)=-9.8t+v_0$ $v=-9.8t+v_0$ $v_0=120$ $v=-9.8t+120$ $5$ seconds later, $v=-9.8(5)+120$ $v=71$ meters per second $10$ seconds later, $v=-9.8(10)+120$ $v=22$ meters per second