About Chanda Walker Expertise I can answer word problems involving mathematics at the high school and college level. I particularly enjoy calculus word problems. Please don't just type the math problem without comments. If you don't tell me what problem your having, I can't help.
Experience Have done word problems as a tutor and as a student of mathematics and physics for years.
Organizations Sigma Xi
Education/Credentials Optical Science PhD
Past/Present Clients I've answered hundreds of questions here at AllExperts.com in algebra, physics and general math sections.
Question I asked everybody these two questions and spent the whole day trying to figure it out. Even my teacher wont explain it because she's "busy". One teacher explained something about completing the square which I know how to do, I just dont know how to apply it to situations like these.
1) When a flare is fired upward at 58.8 m/s, its height, h metres, is given by the equation h = -4.9t^2 + 58.8t, where t seconds is the time since firing.
a) Determine the maximum height of the flare and the time it takes to reach this height.
b) For how many seconds is the flare higher than 98 m?
Anyways I tried it over and over and I know I have to find the roots then the vertex but I dont understand how to apply this equation to find the time the flare is higher than 98 meters. Please help!! Thanks!
Answer If you can find the vertex, then you know the maximum height.
Vertex: (t, hmax)
where t is the time when the h is maximized. T is the time it takes to reach maximum height.
If you want to know how long the flare is higher than 98 then let h = 98.
so 98 = -4.9t^2 + 58.8t
Now solve this for t. You should get two solutions. The small solution is the time when h is 98m on the way up, and the large solution is when h is 98m on the way down.
For the times between those two t's you are above 98m. Just subtract the smaller time from the larger time, and you'll know how long it was above 98m.
I've answered this in instructions not equations and numbers because it seems like that is all you need. If however you need more, just let me know.
I'll try to answer more quickly in reply than I did this time. I forgot my "vacation" had ended. So sorry about the delay.
