Answer:
When t = 25/4 the object his the ground.
Step-by-step explanation:
When the object hit the ground, the distance from it to the ground (or height) will be 0.
Thus,
if when the object touch the ground is when h = 0 then h(t) = 0
So we can set up this equation :
0 = -16t + 100
-100 = - 16t
-100/-16= 25/4 = t