t = 1.4 sec.
This is an example of freefall, here the height is given as function of time and we want to know how long take to the rock from a height of 32m reach the ground.
With h₀ = 32 m, and set h(t) = 0 due the height when the rock hit the ground is 0.
h(t) = -16t² + 32 = 0
Solving:
-16t² + 32 = 0
32 = 16t²
Clear the equation for t:
t = ±√32/16
t = ±1.414s
Take the positivie value since time can't be negative:
t = 1.414s ≅ 1.4s
