SOLUTION: A rock falls off a building, and its position after t seconds of free fall is 269-16t2 feet above the ground. The building is 269 feet tall. a. What is the rock’s velocity at

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Question 28346: A rock falls off a building, and its position after t seconds of free fall is 269-16t2 feet above the ground. The building is 269 feet tall.
a. What is the rock’s velocity at t=3 seconds?
b. How long does it take the rock to hit the ground?
Answer by Paul(988) About Me  (Show Source):
You can put this solution on YOUR website!
Differenitate:
dy%2Fdx=-16%5E2%2B269
=-32x
Lim(-32x) ---> -32(3)=-96
x->3

a) HENCE, the rock's velocity is -96 at 3 second.

b) -16x%5E2=-269
x%5E2=16.8125
x=4.1

Hence, it takes the rock about 4.1 seconds to hit the ground.
Paul.