A child throws his basketball upward from the ground with an initial velocity of 30 ft/sec.

What will be the speed of the ball when it reaches the ground? (I need help uwu)

2 answers

well, clearly
height = -16t^2 + 30t + c, where c is the initial height of the ball when it is released. ( It would be rather difficult for a child to throw the ball upwards from ground level at appr 20 mph, but let's assume c = 0)
then
0 = -16t^2 + 30t
16t^2 - 30t = 0
t(16t-30) = 0
t = 0 (the moment she throws the ball)
or
t = 30/16 = 1.875 seconds

velocity = d(height)/dt = -32t + 30
when t = 1.875, velocity = -32(1.875) + 30 = -30 ft/s

Adjust for any value of c that was given.
where did 16 came from?