Doing physics quiz corrections: One of the questions asks which quantities can be graphed on the x and y-axis that could be used to determine the coefficient of kinetic friction and the answer was to graph height (h) and distance (x) on their respective axis. then the slope (h/x) would be the μk. Why does this happen?

At 20∘c, the hole in an aluminum ring is 2.800 cm in diameter. you need to slip this ring over a steel shaft that has a room-temperature diameter of 2.804 cm . 1. to what common temperature should the ring and the shaft be heated so that the ring will just fit onto the shaft? coefficients of linear thermal expansion of steel and aluminum are 12×10−6 k−1 and23×10−6 k−1 respectively.