It's possible that "WA" is a specific term or abbreviation used within a particular scientific context or research group.
To understand what "WA" means, you'll need more context.
Could you please provide more information?
For example:
* Where did you encounter this abbreviation? (e.g., a textbook, research paper, lecture notes)
* What was the surrounding text?
* What is the broader topic being discussed?
With more information, I can help you decipher the meaning of "WA" in the context of friction.
