Answer:
4.47 seconds.
Step-by-step explanation:
Given function:
[tex]h(t)=-10t^2+200[/tex]
where:
- h is the height (in feet).
- t is the time (in seconds).
The rock will hit the ground when h(t) = 0.
Therefore, set the function to zero and solve for t:
[tex]\begin{aligned}h(t)&=0\\\implies -10t^2+200&=0\\10t^2&=200\\t^2&=20\\t&=\pm\sqrt{20}\\t&=-4.47, 4.47\;\; \sf (2\;d.p.)\end{aligned}[/tex]
As time is positive, t = 4.47 s only.
