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

lilg132

help with question

  • one year ago
  • one year ago

  • This Question is Closed
  1. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    \[v = {g \over k} (1 - e ^{-kt})\] v = velocity g = gravitational constant which is \[9.8 ms ^{-2}\] k = (measured in \[s^{-1}\] t = seconds what is e? in the equation

    • one year ago
  2. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    lanaaa to the rescue :p

    • one year ago
  3. lalaly
    Best Response
    You've already chosen the best response.
    Medals 0

    which course are u taking lilg/?

    • one year ago
  4. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    you know already ee can you help me?

    • one year ago
  5. lalaly
    Best Response
    You've already chosen the best response.
    Medals 0

    differentiation?

    • one year ago
  6. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    i think it involves differentiation

    • one year ago
  7. lalaly
    Best Response
    You've already chosen the best response.
    Medals 0

    this is a differential equation and e^-kt is the homogeneous solution

    • one year ago
  8. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    the value for k (s^-1) is 0.15 the value of t you can say is 1 second

    • one year ago
  9. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    what would it be -kte^-kt?

    • one year ago
  10. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    0? :s

    • one year ago
  11. lalaly
    Best Response
    You've already chosen the best response.
    Medals 0

    I still dont get what ur question is, why did u differentiate that? write down the full question lilg

    • one year ago
  12. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    its really long one minute

    • one year ago
  13. lalaly
    Best Response
    You've already chosen the best response.
    Medals 0

    Take ur time im not leavin:)

    • one year ago
  14. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    It is already known that objects falling under the influence of gravity obey the equations of constant acceleration, with a gravitational constant g (usually taken to be 9.8 ms ^-2) that applies to all objects independent of their size or mass Under more realistic conditions, objects falling through air will quickly reach a state of constant velocity, this velocity, which depends on the size, shape, and mass of the falling object, is called terminal velocity. you are on a team developing parachutes for skydivers the velocity v (in ms^-1) of a typical skydiver after t seconds is modelled by your team using the equation \[v = {g \over k} (1 - e ^{-kt})\] the value of k (measured in s^-1) is used to model the different stages of the skydivers decent. The table shows some values found through the experimentation: TYPE OF MOTION k(s^-1) Human in free fall 0.15 Parachute deployed 2.00 1) use a spreadsheet to plot the changing velocity over the 0 to 3 seconds for a parachutist 2) what is the terminal velocity for the skydiver? theres more questions but yes im stuck on 1 :p

    • one year ago
  15. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    anyone?

    • one year ago
  16. JopHP
    Best Response
    You've already chosen the best response.
    Medals 0

    do u k anything abt Euler's formula ?

    • one year ago
  17. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    no

    • one year ago
  18. JopHP
    Best Response
    You've already chosen the best response.
    Medals 0

    e^x=e^z(cosy + i siny) this is the formula

    • one year ago
  19. lalaly
    Best Response
    You've already chosen the best response.
    Medals 0

    Jop euler cant be used here:S

    • one year ago
  20. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    http://en.wikipedia.org/wiki/Euler%27s_formula

    • one year ago
  21. JopHP
    Best Response
    You've already chosen the best response.
    Medals 0

    WHY?

    • one year ago
  22. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    e^2.00(1 second) = cos(1) + 2sin(1)

    • one year ago
  23. JopHP
    Best Response
    You've already chosen the best response.
    Medals 0

    did it work with u?

    • one year ago
  24. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    that would give me -1.223244275 (btw i made a mistake it should -2sin(1))

    • one year ago
  25. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    so \[{9.8 \over 2.00} (-1.223244275)\]

    • one year ago
  26. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    but shoudn't it be \[{9.8^{-2} \over 2.00^{-1}}(-1.223244275)\]

    • one year ago
  27. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    which gives you -0.02547364171

    • one year ago
  28. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    -0.02547364171^-1

    • one year ago
  29. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    is that right?

    • one year ago
  30. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    which is -39.25626384

    • one year ago
  31. JopHP
    Best Response
    You've already chosen the best response.
    Medals 0

    i think it makes sense But i'm nt sure

    • one year ago
  32. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    but i also forgot to take in account that 2.00 should 2.00^s-1 :S that confuses me the most

    • one year ago
  33. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    Is your question really just what e is?

    • one year ago
  34. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    thats one of my questions but i can see gets taken out using the eulers formula, if thats what im supposed to use in this. but i need help working out question 1 really

    • one year ago
  35. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    if someone can show me how they would write the equation out with the values that would help me understand alot better

    • one year ago
  36. experimentX
    Best Response
    You've already chosen the best response.
    Medals 0

    http://www.wolframalpha.com/input/?i=y+%3D+10%281+-+e^%28-2t%29%29+from+t%3D0+to+5

    • one year ago
  37. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    where did you get 10 from? and what about when it says k is measured in s^-1?

    • one year ago
  38. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    Okay okay. Well, the question of what e is is not too hard. e is a mathematical constant. Its value is approximately 2.71828

    • one year ago
  39. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    ok thanks for that smoothmath

    • one year ago
  40. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    also g = 9.8 ms^-2

    • one year ago
  41. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    Yup. If you want to read more about it or understand why it's important, wikipedia is a good source, as always. http://en.wikipedia.org/wiki/E_(mathematical_constant)

    • one year ago
  42. experimentX
    Best Response
    You've already chosen the best response.
    Medals 0

    just putting arbitrary values ... e is Euler's constant ... your velocity should be increasing with constant acceleration ... but since air resistance is directly proportional to velocity .... after certain velocity .. your velocity remains constant ... just another decay equation!!

    • one year ago
  43. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    {lilg scratches his head}

    • one year ago
  44. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    1) use a spreadsheet to plot the changing velocity over the 0 to 3 seconds for a parachutist

    • one year ago
  45. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    I mean... I'm not fantastic at spreadsheets, but this is a simple problem as long as you are inputting the equation correctly.

    • one year ago
  46. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    what im mainly confused about is when i use these values in the equation FOR EXAMPLE g = 9.8 ms^-2 to put it in the equation as 9.8^-2 or just 9.8

    • one year ago
  47. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    just 9.8 =)

    • one year ago
  48. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    and the same for k when it says it is measured in s^-1 so i should just leave it as 0.15 or 2.00 instead of 0.15^-1

    • one year ago
  49. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    When they say "ms^-2" that's the unit only. \[ms^{-2} = \frac{m}{s^2}\] Which is the saem as "meters per second squared."

    • one year ago
  50. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    also the end result v is in ms^-1 so the end answer e.g. is 20 would i write it as 20^-1 or just 20

    • one year ago
  51. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    Yup. Don't worry too much about the units here =)

    • one year ago
  52. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    ok :)

    • one year ago
  53. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    soooo if you can just check one answer for me if its correct im going to use k = 0.15 and t = 1 second so i would get \[v = {9.8 \over 0.15}(1 + \cos(1) - 0.15\sin(1))\] or is it - cos(1)

    • one year ago
  54. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    Those are units of measurement. If I ask you how much something costs, and you answer "20," I will get angry and ask you "20 WHAT?" Same thing here. Velocity is measured in meters per second, which can be written as \[\frac{m}{s}\]

    • one year ago
  55. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    Oh my god no no no. Ignore that fancy pants crap those other people were giving you. That's just making the problem complicated. Just plug in the right values to the original equation and solve.

    • one year ago
  56. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    can you show me how you would plus in the values in the equation please it will help me understand much better

    • one year ago
  57. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    use the value of k = 0.15 and t = 1 second

    • one year ago
  58. rs32623
    Best Response
    You've already chosen the best response.
    Medals 0

    are u asking the value of e? it is approximately equal to 2.71..

    • one year ago
  59. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    Sure. k = .15 t=1 \[\frac{g}{k}(1-e^{-kt}) = \frac{9.8}{0.15}(1-e^{-0.15*1})\]

    • one year ago
  60. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    Easy peasy. Plug in and solve. Make sure to use the correct order of operations and keep track of signs =)

    • one year ago
  61. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    Still confused?

    • one year ago
  62. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    do i not use eulers formula then?

    • one year ago
  63. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    when i have e^-0.15*1 what do i do with that?

    • one year ago
  64. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    You don't need to, so I don't see why you should.

    • one year ago
  65. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    \[a^{-x} = (\frac{1}{a})^x\]

    • one year ago
  66. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    so would it be \[({1 \over e})^{-0.15}\]

    • one year ago
  67. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    That's the rule for negative exponents. Take the reciprocal and make the exponent positive. Alternatively, you could just put in that expression to a calculator and it'll do the work for you.

    • one year ago
  68. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    Not quite. \[(\frac{1}{e})^{0.15}\]

    • one year ago
  69. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    oh ok yes my mistake

    • one year ago
  70. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    so it would be \[(1 - ({1 \over e})^{0.15})\]

    • one year ago
  71. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    Yessir.

    • one year ago
  72. lilg132
    Best Response
    You've already chosen the best response.
    Medals 0

    thanks alot mate appreciate your great help

    • one year ago
  73. SmoothMath
    Best Response
    You've already chosen the best response.
    Medals 1

    My pleasure =)

    • one year 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.