Chapter 4.1, Problem 93E

Velocity If a stone is dropped from a height of 400 feet, its height s after t seconds is given by $s\left(t\right)=400-16t^2,$ with s in feet.

a. Compute $s^{\prime }\left(t\right)$, and hence find the stone’s velocity at times $t=0,1,2,3,$ and4 seconds.

b. When does the stone reach the ground, and how fast is it travelling when it hits the ground? [HINT: It reaches the ground when $s\left(t\right)=0.$

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