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    Hi, I'm getting confused between equations and was wondering if any one had any advice
    Here's the question I'm attempting :

    A molecule will escape from the Earth when its speed in 11 000 m/s
    Calculate the temperature at which the rms speed of carbon dioxide molecules of mass 7.5x10^-26 kg will reach this speed.

    So I used (C-bar)squared = 3kt/m
    11 000 = 3 x 1.38x10^-23 x t / 7.5 x 10 ^ -26
    this gave me
    T = 11 000 / 552
    T = 20 K

    So what I'm confused with is should i have squared the 11 000 before using it, or is that what csquared is equal to ?
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    (Original post by Roxanne18)
    Hi, I'm getting confused between equations and was wondering if any one had any advice
    Here's the question I'm attempting :

    A molecule will escape from the Earth when its speed in 11 000 m/s
    Calculate the temperature at which the rms speed of carbon dioxide molecules of mass 7.5x10^-26 kg will reach this speed.

    So I used (C-bar)squared = 3kt/m
    11 000 = 3 x 1.38x10^-23 x t / 7.5 x 10 ^ -26
    this gave me
    T = 11 000 / 552
    T = 20 K

    So what I'm confused with is should i have squared the 11 000 before using it, or is that what csquared is equal to ?
    The rms speed is root(bar(c squared)), \sqrt{\bar{c^2}}.

    The equation you were using is \bar{c^2} = \dfrac{3k_BT}{m}
    \bar{c^2} is the square of the rms, so you should square the rms before you substitute into the equation.
 
 
 
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