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anonymous

  • one year ago

guys please help me. I give medals A particle is moving along the x-axis so that its position at t ≥ 0 is given by s(t) = (t)In(3t). Find the acceleration of the particle when the velocity is first zero

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  1. anonymous
    • one year ago
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    @jim_thompson5910

  2. anonymous
    • one year ago
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    To find the time when the particle is first time at the origin, set x(t) = 0. From the nature of cos() function, we know x(t) becomes zero for the first time when t√ equals π2. This gives the time instant. To find the velocity at this time, differentiate x(t) with respect to t to get v(t), and plug in the value of time in the expression for v(t).

  3. anonymous
    • one year ago
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    @triciaal

  4. anonymous
    • one year ago
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    @jim_thompson5910

  5. jim_thompson5910
    • one year ago
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    `Find the acceleration` v(t) = s ' (t) a(t) = v ' (t) = s '' (t) so you'll have to find the second derivative of s(t). Equivalently, the first derivative of v(t)

  6. jim_thompson5910
    • one year ago
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    if s(t) = t*ln(3t), then what is s ' (t) ?

  7. anonymous
    • one year ago
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    so the acceleration is the second derivative right?

  8. jim_thompson5910
    • one year ago
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    yes of the position function

  9. anonymous
    • one year ago
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    ok, give me minute

  10. anonymous
    • one year ago
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    i think it's wrong, but I got 1+ln(3x) for the first derivative

  11. freckles
    • one year ago
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    pretty! Find the acceleration of the particle when the velocity is first zero so you have v=1+ln(3x) you want to find x such that v is 0

  12. freckles
    • one year ago
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    then you find v'

  13. jim_thompson5910
    • one year ago
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    s(t) = t*ln(3t) s ' (t) = d/dt [ t*ln(3t) ] s ' (t) = d/dt [ t ]*ln(3t) + t* d/dt [ ln(3t) ] s ' (t) = 1*ln(3t) + t* (1/3t)*3 s ' (t) = ln(3t) + 1 s ' (t) = 1 + ln(3t) so you have it correct @Joseluess

  14. anonymous
    • one year ago
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    ok, so the secod derivative is 1/x

  15. jim_thompson5910
    • one year ago
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    1/t, yes

  16. anonymous
    • one year ago
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    okay so now do I plug zero ?

  17. freckles
    • one year ago
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    well it says to evaluate the acceleration when the velocity is 0 that is why I asked you to find x such that v is 0

  18. freckles
    • one year ago
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    v=1+ln(3x) 0=1+ln(3x) note: I don't know why it says when the velocity is first 0 because it is only ever 0 once

  19. anonymous
    • one year ago
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    but I have to solve for the acceleration, which is the second derivative.

  20. freckles
    • one year ago
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    yes I know

  21. freckles
    • one year ago
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    but you need to evaluate the acceleration at the value that makes the velocity 0

  22. anonymous
    • one year ago
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    so do i solve for x when velocity is zero?

  23. freckles
    • one year ago
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    yes solve 0=1+ln(3x)

  24. jim_thompson5910
    • one year ago
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    `Find the acceleration of the particle when the velocity is first zero` as freckles is saying, you plug v = 0 into v = 1+ln(3t) and solve for t then you take that t value and plug it into a(t) = 1/t

  25. anonymous
    • one year ago
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    ok, I got stuck I completely forgot how to solve from this part

  26. anonymous
    • one year ago
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    |dw:1440985593903:dw|

  27. anonymous
    • one year ago
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    do I ln both sided to cancel ln ?

  28. freckles
    • one year ago
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    \[\log_b(a)=x \text{ has equivalent exponential form } b^x=a \\ \text{ also note that } \ln(x)=\log_e(x)\]

  29. anonymous
    • one year ago
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    1/3e

  30. jim_thompson5910
    • one year ago
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    yes, \[\Large t = \frac{1}{3e}\] now plug that into a(t)

  31. anonymous
    • one year ago
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    3e

  32. jim_thompson5910
    • one year ago
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    yep, a(t) = 3e is your acceleration when t = 1/(3e)

  33. anonymous
    • one year ago
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    okay, thank you so much..... I'll give it to you the medal, but @freckles I'll make another question and ill give it to you

  34. freckles
    • one year ago
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    no I don't really care I just wanted to help with a calculus problem even though @jim_thompson5910 was already doing an awesome job because lets face it calculus is most fun

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