Problem 8E

8. If a ball is thrown vertically upward with a velocity of $80 \mathrm{ft} / \mathrm{s}$, then its height after $t$ seconds is $s=80 t-16 t^{2}$

(a) What is the maximum height reached by the ball?

(b) What is the velocity of the ball when it is $96 \mathrm{ft}$ above the ground on its way up? On its way down?

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