a. In an experiment to determine the maximum viscous drag of glycerine, a student used a steel ball of diameter 2.0mm together with a column of glycerine held in a tall glass tube blocked at the base. The ball was released to fall along the middle of the column and then timed over a distance of 20cm near the base of the column. The time taken was found to be 2.0 seconds. Explain. i. How the diameter of steel ball was accurately measured.