Initial Velocity

Question

A ball is thrown vertically upward from the top of a 100-foot tower, with an initial velocity of 20 ft/sec. Its position function is s(t) = -16t^2 + 20t + 100. What is its velocity in ft/sec when t = 1 second?

1) -12

2) -44

3) 100

4) -32

Answer 1

Velocity = s'(t)

s'(t) = -32t + 20

For t = 1

s'(1) = -32(1) + 20 = -32 + 20 = -12 ft/sec

Answer: A