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# RMS equation confunsion watch

1. 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 ?
2. (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)), .

The equation you were using is
is the square of the rms, so you should square the rms before you substitute into the equation.

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