Question

A stuntman jumping off a 20-m-high building is modeled by the equation h = 20 – 5t2, where t is the time in seconds. A high-speed camera is ready to film him between 15 m and 10 m above the ground. For which interval of time should the camera film him?

Answer 1

Your answer: 1 ≤ t ≤ √2

Answer 2

Answer: Time interval of camera film him is
`1\leq t\leq √(2)`

Explanation:

Given: A stuntman jumping off a 20-m-high building is modeled by the equation
`h=20-5t^2`, where t is the time in seconds..........(1)

Height of camera to film stunt man is between 15 m and 10 m.

To find interval of time the camera film him, substitute h=15m in (1),we get

`15=20-5t^2\\\Rightarrow-5=-5t^2\\\Rightarrow\ t^2=1\\\Rightarrow\ t=1\text}[time is always positive]{`

Now, substitute h=10m in (1),we get

`10=20-5t^2\\\Rightarrow-10=-5t^2\\\Rightarrow\ t^2=2\\\Rightarrow\ t=√(2)\text}[time is always positive]{`

`\Rightarrow1\leq t\leq √(2)`

Therefore ,time interval of camera film him is
`1\leq t\leq √(2)`