# Quadratic Equations...Problem Solving

Asked Dec 29, 2005, 01:52 PM — 6 Answers
A ball is thrown straight up. Its height, h(in metres), after t seconds is give by h= -5t^2+10t+2. To the nearest tenth of a second, when is the ball 6m above the ground? Explain why there are two answers.

I don't know how to manipulate the formula and how to solve for this problem.

Second question,

The period of a pendulum is the time it takes to swing back and forth, returning to its original position. The relationship between the period, T(in seconds), and the length of the pendulum, L(in metres) is as follows,

T^2 - 4L=0
Correct to the nearest tenth of a second, what is the period of a pendulum 3m long?

Do you use factoring and how?

Thank you.

 CaptainForest Posts: 3,684, Reputation: 2085 Ultra Member #2 Dec 29, 2005, 02:04 PM
Question 1
Formula Given:
H= -5t^2+10t+2

They tell you h=6, find t

So,
-5t^2+10t+2 = h
-5t^2+10t+2 = 6
-5t^2+10t-4=0

Use the Quadratic Equation on the above formula.

X = -b +- sqrroot(b^2-4ac) / 2a

Therefore X, or t = .552786 or t=1.44721

Rounding to the nearest tenth of a second, t = 0.6 and 1.4

Why are there 2 values for t? Because the ball hits the 6m mark on the way up (at t=0.6) and then hits the 6m mark on the way down (at t=1.4)
(Jun 11, 2007 06:20 PM): Comment Deleted   Source:
 Idin89 Posts: 1, Reputation: 1 New Member #3 Mar 8, 2007, 05:14 PM
Research and write a math problem using math in any field of employment. You should exclude the obvious (teachers). Describe how they use math in their field and work through a typical problem. Again, the math must fit an Intermediate Algebra standard and you must state the standard. Make sure if you get an idea from your test that it is a standard for this year. There are topics in the book for scaffolding to other classes so cannot be used since they are not a standard for this year.
Can some one please Help me with this I want to use ( Quadratic Equation)
 hotty707 Posts: 1, Reputation: 1 New Member #4 Mar 8, 2007, 09:10 PM
What is the denominator of each of these decimal numbers when they are written as lowest-terms fractions or mixed numbers?

4.65_____________
.24___________-
 asterisk_man Posts: 476, Reputation: 175 Full Member #5 Mar 9, 2007, 05:53 PM
Both of you should write your questions separately from the original one since they have nothing to do with it. Also, you should not expect us to do your homework questions for you.
 s10762 Posts: 2, Reputation: 10 Junior Member #6 Nov 27, 2010, 07:29 AM
Losers you do not know any thing ! Waste of time ?
 s10762 Posts: 2, Reputation: 10 Junior Member #7 Nov 27, 2010, 07:30 AM
**** off ! I am not going to answer any thing for you

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