# Extension as independent variable?

For a force extension graph of a spring to have extension on the $$x$$ axis means that you change the extension of the spring, and measure the force needed to do that? Why do these exist doesn’t it make better sense to have the force as the $$x$$ variable?

• You choose your reference frame as you see fit, so $x$ and $y$ are basically interchangeable (as long as you stick rigorously to your choice. – Gert May 22 at 20:46
• okay, but if were changing extension, does that mean we measure the force required to do that? – Ubaid Hassan May 23 at 18:32
• No. The choice reference frame doesn't change the force. You make the choice of RF to make the math as simple as possible. The laws of physics aren't affected by it. – Gert May 23 at 22:59