Calculating Helium Vrms and Average KE at 5K

[mastiffcacher]

Homework Statement

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

Homework Equations

Vrms=sqrt((3k_bT)/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/k_b and got 7.21*10^-12. The computer tells me that is wrong also. Where am I messing up?

 

[Redbelly98]

Did you check the units on k_B, T, and m? What values did you use for them?

 

[mastiffcacher]

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.