Rolling rolling rolling
Today one of my first year classes was doing the ball on a slope practical. This is part of a series of practicals designed to introduce students to the skills required for the internal assessment. It involves rolling as small ball down an inclined metal ruler from different heights. One of the aspects of this exercise is the development of understanding of uncertainties and how they can be reduced. The on line clock measures to within 0.001s but repeating runs reveals that there is no point in quoting so many decimal places as the values obtained can vary by up to 1s. The measurements are at first so uncertain, that the difference between runs from different heights is not resolvable, so better technique is required. The main problem seems to be wobble but a careful release method can eliminate this resulting in much more consistent results. Another major improvement is counting down to release eliminating a lot of the reaction time. An an additional aim of this practical is to practice processing data with excel. Don't you just hate it when excel decides that all numbers are dates.
The reason for the annoying date thing is often because students have their computers set so that a comma is a decimal point. If they then enter a number with a full stop as a decimal point excel will think it's a date.