Sketch of Procedure to Measure g by Dropping

Brokk Toggerson

One of the goals of this entire lab course is to get you to think about how to design your own experiments and develop your own procedures. That is part of the reason we keep all the experiments so simple: so that you can really think critically about all the different choices that go into designing an experiment.

In this experiment, you do need a little bit of background information: you probably remember from physics 131 that the height from which you drop a ball is related to the time it takes to fall by  h = \frac{1}{2} gt^2 where  g is the gravitational field. Over the course of this experiment, you are going to have to drop your ball from multiple different heights: you will choose how many. Thus, height is the variable we control, it is the independent variable, and time is the dependent variable. We, therefore, probably want to rearrange this equation so that time is isolated by itself:  t = \sqrt{ \frac{2h}{g} } . Now we’ve got time the dependent variable isolated out by itself and written as a function of our independent variable the height. That is basically the model you are going to be working with:  you are going to be taking your object, dropping it from multiple different heights, and timing how long it takes to hit the ground. Again,  you need to figure out how many different heights to look at. We will guide you through figuring out how many drops to do at each height  – that is part of this lab. You will also have to think about other things like:

  • How are you going to measure the height?
  • Where are you going to do the experiment? I will tell you that the gravitational field changes with location. It is dependent upon how much mass is underneath you. If you’re on top of a big chunk of bedrock, you will get a different answer than if you are sailing on the ocean.

Use your TAs! Have them help you develop your procedure, and remember you’re going to go back in the next lab and redo this experiment thinking about the result you got and how you might improve this procedure. Just sort of keep in the back of your mind as you develop your procedure that you’re going to be refining it for the next lab. Good luck


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Physics 132 Lab Manual by Brokk Toggerson is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License, except where otherwise noted.

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