College

Jerald jumped from a bungee tower. If the equation that models his height, in feet, is [tex]h = -16t^2 + 729[/tex], where [tex]t[/tex] is the time in seconds, for which interval of time is he less than 104 feet above the ground?

A. [tex]t \ \textgreater \ 6.25[/tex]
B. [tex]-6.25 \ \textless \ t \ \textless \ 6.25[/tex]
C. [tex]t \ \textless \ 6.25[/tex]
D. [tex]0 \leq t \leq 6.25[/tex]

Answer :

Sure! Let's solve this problem step-by-step.

We have the equation that models Jerald's height during his bungee jump:
[tex]\[ h = -16t^2 + 729 \][/tex]
where [tex]\( h \)[/tex] is his height in feet and [tex]\( t \)[/tex] is the time in seconds. We need to find out for which interval of time Jerald's height is less than 104 feet.

1. Set Up the Inequality:
We want his height to be less than 104 feet:
[tex]\[ -16t^2 + 729 < 104 \][/tex]

2. Solve the Inequality:
First, let's simplify the inequality:
[tex]\[ -16t^2 + 729 < 104 \][/tex]

Subtract 729 from both sides:
[tex]\[ -16t^2 < 104 - 729 \][/tex]

Which simplifies to:
[tex]\[ -16t^2 < -625 \][/tex]

Divide both sides by -16. Remember, dividing by a negative number flips the inequality sign:
[tex]\[ t^2 > \frac{625}{16} \][/tex]

3. Calculate the Time Intervals:
Now, calculate the square root of [tex]\(\frac{625}{16}\)[/tex]:
[tex]\[ t > \sqrt{39.0625} \][/tex]

Taking the square root gives:
[tex]\[ t > 6.25 \][/tex]
or
[tex]\[ t < -6.25 \][/tex]

However, since time cannot be negative, we discard [tex]\( t < -6.25 \)[/tex].

So, the interval of time during which Jerald is less than 104 feet above the ground is when:
[tex]\[ t > 6.25 \][/tex]

Therefore, the correct answer is:
- [tex]\( t > 6.25 \)[/tex]

I hope this helps! If you have any more questions, feel free to ask.