Since the apple is 16 feet above the ground, we can use the equation of motion for constant gravity to solve for time:
`h=1/2g t^2+v_0t+h_0` where `v_0=0` is the initial speed, and `h_0=16` is the initial height. Also, the final height is h=0. This gives
`0=1/2(-32)t^2+16` simplify multiplication
`0=-16t^2+16` move variable to left side
`16t^2=16` divide by 16
`t^2=1` take square roots
`t=+-1` need positive root for time
It takes 1 second for the apple to fall to the ground.