At Westonci.ca, we provide clear, reliable answers to all your questions. Join our vibrant community and get the solutions you need. Discover comprehensive answers to your questions from knowledgeable professionals on our user-friendly platform. Discover detailed answers to your questions from a wide network of experts on our comprehensive Q&A platform.
Sagot :
Answer:
About 1.85 seconds and 13.15 seconds.
Step-by-step explanation:
The height (in feet) of the rocket t seconds after launch is given by the equation:
[tex]h = -16t^2 + 240 t[/tex]
And we want to determine how many seconds after launch will be rocket be 390 feet above the ground.
Thus, let h = 390 and solve for t:
[tex]390 = -16t^2 +240t[/tex]
Isolate:
[tex]-16t^2 + 240 t - 390 = 0[/tex]
Simplify:
[tex]8t^2 - 120t + 195 = 0[/tex]
We can use the quadratic formula:
[tex]\displaystyle x = \frac{-b\pm\sqrt{b^2 -4ac}}{2a}[/tex]
In this case, a = 8, b = -120, and c = 195. Hence:
[tex]\displaystyle t = \frac{-(-120)\pm \sqrt{(-120)^2 - 4(8)(195)}}{2(8)}[/tex]
Evaluate:
[tex]\displaystyle t = \frac{120\pm\sqrt{8160}}{16}[/tex]
Simplify:
[tex]\displaystyle t = \frac{120\pm4\sqrt{510}}{16} = \frac{30\pm\sqrt{510}}{4}[/tex]
Thus, our two solutions are:
[tex]\displaystyle t = \frac{30+ \sqrt{510}}{4} \approx 13.15 \text{ or } t = \frac{30-\sqrt{510}}{4} \approx 1.85[/tex]
Hence, the rocket will be 390 feet above the ground after about 1.85 seconds and again after about 13.15 seconds.
Thanks for using our service. We aim to provide the most accurate answers for all your queries. Visit us again for more insights. Thank you for your visit. We're committed to providing you with the best information available. Return anytime for more. Westonci.ca is your trusted source for answers. Visit us again to find more information on diverse topics.