From the top of a building, a rock is thrown straight up with an initial velocity of 32 feet per second. The equation s=-16t^2+32t+48 gives the height s of the rock t after it is thrown.

Question

Solve for the time it takes the rock to hit the ground.

Answer 1

When the rock hits the ground s=0 so -16t^2 +32t +48 = 0 divide both sides by -16

t^2-2t -3 =0

(t-3)(t+1) = 0 so t =3

t= -1 is also a solution to the equation but does not make sense in the context of the question as this would require you to go back in time