Question

A ball is thrown vertically upward from the top of a 100 foot tower, with an initial velocity of 10 ft/sec. Its position function is s(t) = –16t2 + 10t + 100. What is its velocity in ft/sec when t = 2 seconds?

Answer 1

All you need to know is that velocity is the derivative with respect to time of position.

Therefore: ds/dt = -32t +10

To know the velocity at t=2s you just need to plug t=2 for t in the equation above.