Quantcast

Got Homework?

Connect with other students for help. It's a free community.

  • across
    MIT Grad Student
    Online now
  • laura*
    Helped 1,000 students
    Online now
  • Hero
    College Math Guru
    Online now

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

heathernelly Group Title

:)

  • 2 years ago
  • 2 years ago

  • This Question is Closed
  1. JakeV8 Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    Is this actually a physics or math project or just a question asking for you to solve for the variable "t"?

    • 2 years ago
  2. JakeV8 Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    you can use basic algebra to solve for t by isolating it, but it will be an equation using L. But that might be all you need to do... sort of depends on what the purpose of this question is.

    • 2 years ago
  3. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    just have to solve for t.. i think :/ sorry my computer is lagging!

    • 2 years ago
  4. JakeV8 Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    \[L = \frac{ 980t^{2} }{ 4\pi^{2} }\]

    • 2 years ago
  5. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    yeah, that's it :)

    • 2 years ago
  6. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    here is an example http://www.khanacademy.org/math/algebra/solving-linear-equations-and-inequalities/v/solving-for-a-variable The first step is multiply both sides by 4\(\pi\). Can you do that?

    • 2 years ago
  7. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    The first step is multiply both sides by 4\(\pi^2\). Can you do that?

    • 2 years ago
  8. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    hmm, not really.. :///

    • 2 years ago
  9. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    write \(4 \pi^2\) times on both sides of the equation

    • 2 years ago
  10. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    okay

    • 2 years ago
  11. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    like i dont understand it because it has the pi? :/ i suck at math

    • 2 years ago
  12. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    pi is just a number if you multiply both sides by 4 pi^2 you get \[ 4 \pi^2 L = 4 \pi^2 \cdot \frac{980 t^2}{4 \pi^2}\]

    • 2 years ago
  13. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    now use a simple rule: if you see something divided by itself , it becomes 1. Does that ring a bell? It makes the right side "simplify"

    • 2 years ago
  14. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    no it doesnt :(

    • 2 years ago
  15. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    ahhh, this is confusing to me

    • 2 years ago
  16. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    Here are some examples \[ 3\cdot \frac{4}{3} = \frac{3\cdot 4}{3}= \frac{\cancel{3}\cdot 4}{\cancel{3}}=4\]

    • 2 years ago
  17. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    do you see anything in your problem that "cancels"?

    • 2 years ago
  18. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    yeah, i get that but it has the pi in the one im doing? :/

    • 2 years ago
  19. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    so the pi would cancel out?:S:/

    • 2 years ago
  20. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    \[ 4 \pi^2 L = \cancel{4 \pi^2} \cdot \frac{980 t^2}{\cancel{4 \pi^2}} \]

    • 2 years ago
  21. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    yeaah, thats what i thought :))

    • 2 years ago
  22. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    it is a good rule to remember. now multiply both sides by \(\frac{1}{980} \)

    • 2 years ago
  23. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    one over what? i can't read that:((

    • 2 years ago
  24. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    1/980

    • 2 years ago
  25. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    first write it down: \[ 4 \pi^2 L \cdot \frac{1}{980}= 980t^2 \cdot \frac{1}{980} \]

    • 2 years ago
  26. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    k 1 sec

    • 2 years ago
  27. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    okays (:

    • 2 years ago
  28. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    the 980's cancel on the right side, right? (that is why we did this) we get \[ t^2 = \frac{4\pi^2 L}{980} \] Do you see how we did that?

    • 2 years ago
  29. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    ohhh, yeah i did

    • 2 years ago
  30. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    the 4 pi^2 L is on the top, and when we multiply fractions, it is top times top and bottom times bottom

    • 2 years ago
  31. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    \[ \frac{4 \pi^2 L}{1} \cdot \frac{1}{980} = \frac{4 \pi^2 L\cdot 1}{1 \cdot 980} = \frac{4 \pi^2 L}{980}\]

    • 2 years ago
  32. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    I would simplify by dividing the top by 4, and the bottom by 4. Can you do that?

    • 2 years ago
  33. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    all of the top?:S i dont know how to simplify because the pi is there? do i use 3.14?:/

    • 2 years ago
  34. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    leave pi alone. if you divide the top by 4 it is doing this \[ \frac{\cancel{4}\pi^2L}{\cancel{4}}\]

    • 2 years ago
  35. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    now divide the bottom by 4: 980/4 is 245 we get \[ t^2= \frac{\pi^2 L}{245} \]

    • 2 years ago
  36. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    do you know how to "solve" for t?

    • 2 years ago
  37. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    multiply both sides by 245?:S

    • 2 years ago
  38. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    im not sureee :(

    • 2 years ago
  39. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    if you multiply both sides by 245 you would get a 245t^2 (making it more "complicated" ) Have you heard of a square root?

    • 2 years ago
  40. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    yeaah i have

    • 2 years ago
  41. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    square roots are how you "undo" squares: \[ \sqrt{x^2}= x\]

    • 2 years ago
  42. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    I would take the square root of both sides

    • 2 years ago
  43. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    can you draw it out for me so i can see what you mean? it makes more sense when you do that:D

    • 2 years ago
  44. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    I've noticed it's easier to do work when someone else is doing it, too. try, it won't hurt

    • 2 years ago
  45. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    it really does help when someone else shows you, but ill draw it on here to see if im right :) im prob not thou ...haha

    • 2 years ago
  46. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    Just draw a big square root over each side

    • 2 years ago
  47. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    |dw:1354152167387:dw|

    • 2 years ago
  48. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    yes, by the t^2 is inside the root sign. and so is the 245. now use the idea that sqrt(x^2) is x so sqrt(t^2) is ?

    • 2 years ago
  49. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    245? haha.. im not sure :/ or 15? :S

    • 2 years ago
  50. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    no, not a number. square root of x*x is x square root of t*t is t (I guess you have to memorize that) we get \[ t= \sqrt\frac{ \pi^2 L}{245} \]

    • 2 years ago
  51. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    now, you can "simplify" (just to show off how much math you know) use the rule that sqrt(a * b) is the same as sqrt(a) * sqrt(b) so the top is sqrt(pi^2) * sqrt(L) you can simplify sqrt(pi^2) , right?

    • 2 years ago
  52. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    yes?.....

    • 2 years ago
  53. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    use the same rule as for sqrt(x^2) (or sqrt(t^2) for that matter)

    • 2 years ago
  54. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    i dont understand when you say sqrt)x^2) really..

    • 2 years ago
  55. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    we start with \[ t= \sqrt\frac{ \pi^2 L}{245} \] we can "break up" the square root by separating it: \[ t = \frac{ \sqrt{\pi^2}\sqrt{L}}{\sqrt{245}} \] the rule "sqrt(x^2) = x means when you see "something" to the 2nd power inside a square root , you can replace it with just "something" There is a good reason to learn this, but first what is \[ \sqrt{\pi^2} \] ?

    • 2 years ago
  56. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    or, another way to think of it, sqrt undoes the square

    • 2 years ago
  57. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    ooh, that kinda makes more sense. what do you mean what is it?

    • 2 years ago
  58. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    so it would be pi^2?

    • 2 years ago
  59. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    or sqaure root pie? :S

    • 2 years ago
  60. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    or neither? hahaa

    • 2 years ago
  61. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    sqrt(pi^2) is not pi^2 (that would mean sqrt is doing nothing) sqrt(pi^2) is not sqrt(pi) (that would mean pi^2 is the same as pi) sqrt(pi^2) "makes the square go away"

    • 2 years ago
  62. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    if \[ \sqrt{x^2}= x\] and \[ \sqrt{t^2}=t\] what is \[ \sqrt{\pi^2}= ?\]

    • 2 years ago
  63. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    pi..lol

    • 2 years ago
  64. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    yes, so now you have \[ t = \frac{ \sqrt{\pi^2}\sqrt{L}}{\sqrt{245}} \] \[ t = \frac{ \pi\sqrt{L}}{\sqrt{245}} \] finally we can rewrite sqrt(245) as sqrt(5*7*7) or \[ \sqrt{7^2}\cdot \sqrt{5} \] do I dare ask what is sqrt(7*7)?

    • 2 years ago
  65. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    hahah!

    • 2 years ago
  66. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    49

    • 2 years ago
  67. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    7*7 = 49 but sqrt(7*7) is 7 (or sqrt(49) is 7) 7*7 is 7^2 and the square root undoes the square.

    • 2 years ago
  68. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    yeaah

    • 2 years ago
  69. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    we now have \[ t = \frac{ \pi\sqrt{L}}{\sqrt{245}} \] \[ t = \frac{ \pi\sqrt{L}}{7\sqrt{5}}

    • 2 years ago
  70. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    \[t = \frac{ \pi\sqrt{L}}{7\sqrt{5}} \]

    • 2 years ago
  71. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    The last step. People (why?) do not like sqrt in the denominator, so we multiply top and bottom by sqrt(5) \[ t = \frac{ \pi\sqrt{L}}{7\sqrt{5}}\cdot \frac{\sqrt{5}}{\sqrt{5}}= \frac{ \pi\sqrt{5L}}{35}\]

    • 2 years ago
  72. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    that is your answer

    • 2 years ago
  73. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    wow, that is a loooot of work!! but thank you so much.. when i re-read over it tomorrow, i'll prob be awesome at it ;) haha....ill prob get it! :D are you a teacher?

    • 2 years ago
  74. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    The reason you learn this is to 1. See if you *can* learn it. 2. If you can learn it, it changes how you think (in a good way)

    • 2 years ago
  75. phi Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    I am an engineer for a living..

    • 2 years ago
  76. heathernelly Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    thats awesome :D

    • 2 years ago
    • Attachments:

See more questions >>>

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.