I have been investigating the damping of an oscillating mass on a spring by a piece of card of varying surface area, in order to work out the damping constant λ for the equation y = A₀ e-λt sin(ωt). I took the natural log of the amplitude of each successive oscillation and plotting that against time elapsed to give a graph of ln(y) = -λt + ln(A₀), so I could take the gradient and obtain a value for λ. I then plotted a graph of my values for λ against the surface area of the card. I was expecting a linear relationship between λ and surface area, but instead obtained the non-linear graph I have attached. https://www.physicsforums.com/attachments/screen-shot-2014-11-16-at-20-33-26-png.75536/ [Broken] Why is this the case? How can I explain this?