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Another Physics Question

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  • 18-02-2010 10:27am
    #1
    entropic
    Closed Accounts Posts: 172 ✭✭


    I know you have been inundated with homework questions recently but I have been absolutly stumped by this and I cant get the answer no matter what method I use.

    An interstellar cloud, made up of an
    ideal gas, collapses with its radius
    decreasing as

    R
    = 1013(-t/216)^2/3

    with t measured in years. The time t

    is taken to be zero at zero radius so
    that t is always negative. The cloud
    collapses isothermally at 10 K until its
    radius reaches 1013 m. It then becomes
    opaque so that, from then on, the
    collapse takes place adiabatically (gammma=5/3) and reversibly. How many years does
    it take for the temperature to rise by
    800 K measured from the time the cloud
    reaches a radius of 1013 m.

    I have tried mainly the adiabtic relationship for temperature T(V^GAMMA-1)= Constant to imply that T1(V1^y-1)=T2(V2^y-1) taking the time at T1V1 to be 216 years and assuming the could is a sphere.
    I have also tried integrating the formula for R as I thought it may need to be if its the rate of change of the radius.
    I know the answer is 208 Years (Back of the book answer) but so far I have not been able to get that. Any help or pointers in the right direction would be greatly appreciated.


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    #2
    10DKing
    Closed Accounts Posts: 1 ✭10DKing


    Hi what is the name of the book you got this problem from??


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