Answer :
Question 1 : Janae can find out when she first hit the water by finding out the distance of travel, as well as her speed of travel
Question 2 :
Given that her height above the water can be modeled using the function below:
[tex]f(x)=-5x^2\text{ + 10x + 15}[/tex]We can obtain her vertical distance of travel from the diving board to the point where she starts to descend
At the turning point,
[tex]\frac{df(x)}{dx}\text{ = 0}[/tex][tex]\begin{gathered} \frac{df(x)}{dx}\text{ = 10x + 10 = 0} \\ x\text{ = -1} \\ \text{substituting back into f(x)} \\ f(-1)=5(-1)^2\text{ + 10(-1) + 15} \\ =\text{ 5 - 10 + 15} \\ =\text{ 10} \end{gathered}[/tex]Hence, Jane travelled a distance of 10 units upwards and (10 + 15)unit downwards
At the turning point, her velocity is zero, using the relation below we can find her initial velocity and then the time it took
[tex]\begin{gathered} v^2=u^2\text{ - 2gS} \\ 0=u^2\text{ - 2 }\times\text{ 10 }\times10 \\ u\text{ = 14.14 m/s} \\ v\text{ = u - gt } \\ 0\text{ = 14.14 - 10 }\times\text{ t} \\ t\text{ = 1.414s } \end{gathered}[/tex]From the turning point, her velocity changes from 0