Question

Draco steals and throws Neville's red ball straight up at 54 feet per second from about 7 feet above the ground. The ball's height in feet above the ground after tt seconds is given by

h(t)=â16t2+54t+7

How long does he have until the ball reaches the ground? seconds

Answer 1

3.5

Explanation:

The ball reaches the ground when
`h(t)=0`.

`-16t^2+54t+7=0 \\ \\ 16t^2-54t-7=0 \\ \\ (8t+1)(2t-7)=0 \\ \\ t=-1/8, t=7/2 \\ \\ t>0 \implies t=3.5`