Recap the last lab

Welcome to this next lab where you’re actually going to do the same experiment: dropping an object to measure the strength of the earth’s gravitational field . Why are we doing the same experiment twice? To answer that question, we should think about some of the problems with the last lab. Some of the challenges that we faced were that the linear fit that you did, ordinary least squares, does not include uncertainties in any way. A rather significant omission for a lab part of the purpose of which is to really understand and learn how to manage uncertainties. The second problem is that, in the last lab, we completely ignored any uncertainty in the drop height. The logic was that the uncertainty of the drop height would be small relative to the uncertainty in the fall time and so it was probably OK to ignore it. For a more complete picture, however, we should at least quantify the uncertainty in the drop height. Finally, your result from the last time might not have been as close to the “true” value of about 9.8 N/kg as you might hope. That is OK! I mentioned in the last lab that it’s alright to not get the “true” answer, but being off shows that there’s always room to improve. Improving measurements is another big part of this series of lab: refining your procedures by thinking critically, understanding your uncertainties, and using that knowledge to refine your procedures. So, before we talk anymore about what we’re going to do in this particular lab, let’s go back and refresh what you did last time and quantify the problems from the last lab.