The magnetic barrier apparatus is placed on a gram scale, which is in turn placed on an aluminum lab jack lift set to the lowest position, and placed on the base of a lab stand. The upper array is removed from the apparatus leaving the plastic straw in the lower array. The scale is then tared. Using the graduated plastic straw as a guide, the upper magnet array is aligned above the lower array and secured by a non-magnetic clamp. Care must be taken to align the magnetic poles (arrows). The initial scale value is recorded. The lift is raised 1 cm at a time and the scale value is recorded at each height. When the arrays are separated by a distance of 2 cm, measurements are recorded every 1 mm. Three trials are performed, and the average values at each distance are determined. These average values are converted to force in newtons (grams are converted to kilograms, then multiplied by the acceleration of gravity, 9.8 m/s 2 ). A force/distance curve is plotted, and the distance at which force is at a maximum indicates 𝒉 𝟏 , the height of the magnetic potential barrier (Figure ).