when h(t)=0, it hits the ground
solve
0=-16t^2+24
factor out -8
0=-8(2t^2-3)
we know that
0=2t^2-3 since factors have to multiply to 0
add 3 to both sides
3=2t^2
divide both sides by 2
1.5=t^2
sqrt both sides
1.2247=t
after about 1.2247 seconds it will hit the ground
