Question

If a ball is thrown into the air with a velocity of 39 ft/s, its height (in feet) after t seconds is given by y = 39t − 16t2. find the velocity when t = 1.

Answer 1

For this case we have the following equation:
y = 39t - 16t2
Deriving we have that the speed is given by:
v = 39 - 32t
Evaluating the speed for t = 1 we have:
v = 39 - 32 (1)
v = 39 - 32
v = 7 feet / s
Answer:
the velocity when t = 1 is:
v = 7 feet / s