I need help with this question asap!!!!

Question

When an object is dropped form a height of s feet above the ground the height h of the object is given by the equation h=-16t²+s where t is the time in seconds after the object has dropped. If an object is dropped from a height of 144 feet above the ground how many seconds will it take to hit the ground?

Can you please show the steps so I can understand?

Answer 1

h = -16t^2 + s

h is zero when it hits the ground

s starting out at 144 feet, therefore by substitution we get

0 = -16t^2 + 144, add 16t^2 to both sides

16t^2 = 144, divide by 16

t^2 = 9, square root

we get t = 3 and t = -3, negative 3 is not a viable answer. So the object will hit the ground after three seconds.

Answer 2

h = - 16t² + s;

When obgect hit ground h = 0, so s - 16t² = 0; 144 - 16t² = 0; 16t² = 144; t² = 9; t = 3 s.