Find the instantaneous velocity At a time $t$ seconds after it is thrown up in the air, a tomato is at a height of $f(t) = −4.9t^2 + 25t + 9$ meters.
Find the instantaneous velocity of the tomato at $t = 1.8$.

Speed of the tomato is just $f'$.
$$
f'(t) = -9.8t + 25
$$
Now we can get the speed at $t = 1.8$:
$$
f'(1.8) = -9.8 \cdot 1.8 + 25 = 7.36
$$
