Wednesday

October 22, 2014

October 22, 2014

Posted by **Anonymous** on Monday, February 25, 2013 at 12:55am.

Do I set it up like this?

-9.8(1)^2+88.2(1)+137.2 = 215.6

Then h=b/2a=9.8/215.6=22m

137.2+22=159

Thanks for your help.

- college algebra -
**Steve**, Monday, February 25, 2013 at 12:30pmNot quite. You found (sort of) when the height is greatest (the vertex of the parabola). That was not the question.

You have

h=-9.8t^2+88.2t

when is h=137.2?

(Aside. You sure about that 9.8? h = vt - 1/2 at^2 and a = 9.8)

137.2 = -9.8t^2 + 88.2t

t = 2,7

So, at those two times, h=137.2

Knowing what you do about the shape of parabolas, and that this one opens downward, h > 137.2 between those two values, so

2 < t < 7

**Answer this Question**

**Related Questions**

algebra - If a rocket is propelled upward from ground level, it's height in ...

math-algebra - A launched rocket has an altitude, in meters, given by the ...

Algebra~Scary problem! - A launched rocket has an altitude, in meters, given by ...

Physics - A test rocket is launched vertically from ground level (y=0m), at time...

Math - A rocket follows a parabolic trajectory. After t seconds, the vertical ...

college algebra - A model rocket is launches upward with an initial velocity of ...

algebra - A launched rocket has an altitude, in meters,give n by the polynomial ...

algebra - the path of a rocket fired during a fireworks display is given by the ...

Math - A rocket is launched upward and then falls to the ground. The height of ...

Math/calculus - a toy rocket is shot into the air at the top of a building so ...