Question

**A rock dropped from a 100 foot tower.

Answer 1

Answer:

2.83 s

Step-by-step explanation:

We are given that

$h(t)=-16t^2+10t+100$

When a rock reached the ground then h(t)=0

$-16t^2+10t+100=0$

$16t^2-10t-100=0$

Using quadratic formula

$x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$

$t=\frac{10\pm\sqrt{(-10)^2-4\times 16\times (-100)}}{2(16)}$

$t=\frac{10\pm\sqrt{100+6400}}{32}$

$t=\frac{10+\sqrt{6500}}{32}=2.83$

$t=\frac{10-\sqrt{6500}}{32}=-2.2$

Time cannot be negative .Therefore, negative value of t can not be possible.

Hence, the rock takes 2.83 sec to reach the ground.