SOLUTION: A model rocket is launched upward with an initial velocity of 240 feet per second. The height, in feet, of the rocket t seconds after the launch is given by h = −16t2 + 240t.

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Question 1186597: A model rocket is launched upward with an initial velocity of 240 feet per second. The height, in feet, of the rocket t seconds after the launch is given by
h = −16t2 + 240t.
How many seconds after the launch will the rocket be 340 feet above the ground? Round to the nearest tenth of a second.
Answer by ikleyn(53937) About Me  (Show Source):
You can put this solution on YOUR website!
.

To answer the question, you need solve this quadratic equation


    -16t^2 + 240t = 340.


You will get two roots:  one works for ascending move;  the other works for descending move.



ANSWER.  t = 1.584  seconds;   t = 13.42 seconds.


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In this site,  there is a bunch of lessons on a projectile thrown/shot/launched vertically up
    - Introductory lesson on a projectile thrown-shot-launched vertically up
    - Problem on a projectile moving vertically up and down
    - Problem on an arrow shot vertically upward
    - Problem on a ball thrown vertically up from the top of a tower
    - Problem on a toy rocket launched vertically up from a tall platform

Consider these lessons as your textbook,  handbook,  tutorials and  (free of charge)  home teacher.
Read them attentively and learn how to solve this type of problems once and for all.

Also,  you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this textbook under the topic "Projectiles launched/thrown and moving vertically up and dawn".


Save the link to this online textbook together with its description

Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson

to your archive and use it when it is needed.