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**sid2010** AP Calculus help anyone?

1.Use the position function s(t) = -16(t)^2 + vo(t) + so for free- falling objects.

Question - A ball is thrown straight down from the top of a 220-foot building with an initial velocity of -22 feet per second. What is its velocity after 3 seconds? What is its velocity after falling 108 feet?

$\displaystyle \textcolor{red}{s(t) = -16t^2 - 22t + 220}$

v(t) = s'(t)

2. Use the position function s(t) = -4.9(t)^2 + vo(t) + so for free falling objects.

Question - To estimate the height of a building, a stone is dropped from the top of the building into a pool of water at ground level. How high is the building if the splash is seen 6.8 seconds after the stone is dropped?

$\displaystyle \textcolor{red}{0 = -4.9(6.8)^2 + s_0}$

$\displaystyle \textcolor{red}{s_0}$ is the building's height

I'm in calculus AP, and I'm really uncomfortable with velocity problems. Help please?