If an object is dropped from a height of 144 feet, the function gives the height of the object after t seconds. when will the object hit the ground?

A=-32  (acceleration is the constant g)  integrating with respect to t

v=-32t+vi  but initial velocity is equal to zero as it is just "dropped".

h=-32t^2/2+hi, since the initial height is 144 ft

h(t)=-16t^2+144

The object will be at the ground when h(t)=0

-16t^2+144

-16(t^2-9)=0  

-16(t+3)(t-3)=0, but since we know t>0

t=3 seconds.