Calculating Helium Vrms and Average KE at 5K

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SUMMARY

The root mean square speed (Vrms) of Helium at 5K is calculated using the formula Vrms=sqrt((3kbT)/m). The user initially calculated Vrms as 7.19×10-12 but received an incorrect response. The average kinetic energy (KE) was found to be 1.04×10-22 using the formula 2/3 Kavg/kb, which also returned an incorrect result. The issue was identified as a unit conversion error, specifically converting atomic mass units (amu) to kilograms (kg).

PREREQUISITES
  • Understanding of the ideal gas law and kinetic theory of gases
  • Familiarity with the Boltzmann constant (kb) and its units
  • Knowledge of unit conversions, particularly from amu to kg
  • Basic proficiency in algebra for manipulating equations
NEXT STEPS
  • Review the calculation of root mean square speed using the formula Vrms=sqrt((3kbT)/m)
  • Study the relationship between temperature and average kinetic energy in gases
  • Learn about unit conversions, specifically converting amu to kg for gas calculations
  • Explore the implications of temperature on molecular speed and kinetic energy in different gases
USEFUL FOR

Students studying thermodynamics, physics enthusiasts, and anyone involved in gas behavior calculations at low temperatures.

mastiffcacher
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Homework Statement



What is the root mean square speed of Helium at 5K?

Homework Equations



Vrms=sqrt((3kbT)/m)

The Attempt at a Solution



I plugged all the numbers in and keep getting 7.19*10-12. The computer keeps telling me that it is not correct. The next question ask for the avg KE which I found to be 1.04×10−22. I tried using 2/3 Kavg/kb and got 7.21*10-12. The computer tells me that is wrong also. Where am I messing up?
 
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Did you check the units on kB, T, and m? What values did you use for them?
 
That is the whole proble. I remember overhearing the professor and another student talking about converting amu to kg. I plugged in the conversion and got the answer. It has been a long week and day. Guess my brain is still fried from the calculus test tonight. Thanks for the help.
 

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