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Math Help - Mass along a wire?

  1. #1
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    Mass along a wire?

    I have no idea how i should solve this problem..

    http://snag.gy/L6hWl.jpg

    Please help.. I seriously have no idea..
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  2. #2
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    Re: Mass along a wire?

    From the definition of dr
    dr= dxi+ dyj+ dzk

    Take the magnitude of dr
    |dr|^2= (dx)^2+ (dy)^2+ (dz)^2

    (\frac{|dr|}{dt})^2= (\frac{dx}{dt})^2+ (\frac{dy}{dt})^2+ (\frac{dz}{dt})^2

    You can find the values of \frac{dx}{dt},\frac{dy}{dt} and \frac{dz}{dt} in terms of t easily. Then get |dr| on its own and integrate it between t=0 and t=1

    Edit. Didnt see that the density wasn't constant.
    After you get an expression for dr in the form |dr|=g(t)dt since the density is 1+t find the integral of (1+t)g(t)dt between 0 and 1
    Last edited by Shakarri; March 11th 2013 at 09:41 AM.
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  3. #3
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    Re: Mass along a wire?

    After you get an expression for dr in the form |dr|=g(t)dt?..

    what do you mean by numeric form of it, and g(T)?
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  4. #4
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    Re: Mass along a wire?

    m=int(density*sqrt((x'(t))^2+(y'(t))^2+(z'(t))^2)d t
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  5. #5
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    Re: Mass along a wire?

    Quote Originally Posted by peysy View Post
    m=int(density*sqrt((x'(t))^2+(y'(t))^2+(z'(t))^2)d t
    This is the length of the wire not the mass
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  6. #6
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    Re: Mass along a wire?

    Quote Originally Posted by peysy View Post
    m=int(density*sqrt((x'(t))^2+(y'(t))^2+(z'(t))^2)d t
    This is the length of the wire not the mass
    No, with that "density" function in there, it is the mass.
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  7. #7
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    Re: Mass along a wire?

    density=(1+t) g/u =)
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  8. #8
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    Re: Mass along a wire?

    Quote Originally Posted by HallsofIvy View Post
    No, with that "density" function in there, it is the mass.
    I realise that. I included the density function in the integration in my first reply, I was preventing op from getting muddled between the two answers.
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