A ball is thrown vertically upward from the top of a building 96feet tall with an initial velocity of 80feet per second. The distance S (in feet )of the ball from the ground, after t seconds is s=96+80t-16tsquard.

(a)After how many seconds does the ball strike the ground?

When s = 0 it hits the ground

s=96+80t-16t^2 = 0

-t^2 + 5t + 6 = 0

(-t + 6)*(t + 1) = 0

t = -1 second (Ignore)

t = 6 seconds to impact

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(b) After how many seconds will the ball pass the top of the building on its way down?

96+80t-16t^2 = 96

-t^2 + 5t = 0

t = 0 (at launch)

t = 5 seconds (on the way down)