Question

A stuntman jumping off a 20-m-High building is modeled by the equation h=20-5t^2, where t is the same in seconds. A high-speed camera is ready to film him between 15m and 10m above the ground. For which interval of time should the camera film him?

Answer 1

Answer: $1\leq t\leq \sqrt{2}$

Step-by-step explanation:

1. You know that the high-speed camera is ready to film him between 15 meters and 10 meters above the ground.

2. The problem gives you the following equation:

$h=20-5t^{2}$

3. Therefore, you must calculate the time when $h=15$ and when $h=10$, as following:

$h=15\\15=20-5t^{2}\\5t^{2}=5\\t=\sqrt{1}\\t=1$  

$h=10\\10=20-5t^{2}\\5t^{2}=10\\t=\sqrt{2}$

4. Therefore, the answer is:

$1\leq t\leq \sqrt{2}$