Question

"A description of the physics used to tune the instrument" Physics class unformal lab, we built our own instruments and I made a guitar. What is the description?

Answer 1

Is the idea to describe how you tuned your guitar and what was
happening physically as you tuned it?

I mean, typically, you'd be tuning a guitar by tightening and loosening its strings, and in so doing, you are adjusting the tension in the guitar strings.
The higher the tension in the strings, the higher the speed of the wave generated by plucking the string, and the higher the frequency of the wave generated.

A higher frequency wave generated on the string corresponds with a sound of higher pitch.
So if the note you heard on your guitar sounded flat (unusually low pitch), then you'd tune the guitar by tightening the string.

Answer 2

If the note you heard on your guitar sounded sharp (unusually high pitch), then you'd tune the guitar by loosening the string.

The physics there is true. I'm hoping it's the answer to the question they were asking!