Day Four – Measuring gravity using a free-fall apparatus and plotting a graph in Microsoft Excel.

May 31, 2007 3:56 pm
posted by john

Firstly, we decided on the experiment that I was going to do. We chose to do an experiment to measure gravity, g, using the free-fall method.

The apparatus was set up as shown. The experiment was first done with a large ball-bearing, and then with a smalller bearing. Basically, the bearing is held in place in the clamp at a known, measured distance, s. When you release the bearing, it falls and hits the trapdoor underneath. Everything is connected in a circuit to a timer. When the ball hits the trapdoor and the circuit is broken, the timer stops and the amount of time that it took, t, for the ball-bearing to land can be measured. This is done once more, and the lesser of the two is used. To find g, the formula 2[s/t2] is used. This is repeated at a number of different distances and an average value for gravity is found.
This was then repeated with the small ball-bearing.

The average value that I found for g was 9.6 m s-2, the true answer being 9.8 m s-2.

I then learned how to plot my results on Microsoft Excel, a skill that might come in very handy in college! This is a photo of my fully plotted and labelled graph, with distance on the Y axis and time on the X axis.

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