“Real Graphs from Real Data” – an IOP workshop session

I was at the ASE Conference in Liverpool last week (my first ASE conference and first time in Liverpool!). There were so many useful talks and workshops that I frequently wanted to be in three or more places at once – I strongly recommend it if you haven’t been lucky enough to go yet.

The Institute of Physics in particular ran a huge number of high quality sessions, mostly workshops for practical activities, and I’ll use this post to share the ideas from one of them. (Thanks to Alex Birchmore for taking notes in this session and sharing them with me).

“Real Graphs from Real Data”

The session started with attendees contributing activity ideas for teaching reliability, repeats, precision and taking measurements, for example devising ways of measuring the thickness of paper, the mass of grain of rice, the time taken for cart to roll down track, etc. We were then introduced to a new activity idea along the same lines.

Equipment needed: Per group: 1 x A3 paper; 1 x A4 card; 5 x plastic or polystyrene cups with a hole cut in each of the rims; 1 x aluminium ruler (with ridge down the centre); 1 x marble.

Setting up: Fold the A4 card into a triangle and lean the ruler on it to make a ramp. Rest the other end of the ruler on the A3 paper, on which you draw the axes of a graph.

The investigation runs by positioning a plastic/polystyrene cup at the bottom of the ramp with the hole facing the ramp. You roll the marble down the ramp, it goes into the hole, hits the inside of the cup and moves it along the graph. Mark where it ended up, then repeat – inevitably the result is slightly different every time.

The independent variable can then be ‘number of cups’. You repeat the procedure with the cups stacked up, and the more cups you have the smaller the distance they travel along the graph.

I really liked this activity because of how quick, simple and fun it was, with potentially such a lot of learning opportunities.

Potential uses and discussion points

  • Modelling good graph drawing
  • Control variables – ask students to identify what they ought to keep the same each time (e.g. angle of ramp)
  • ‘True value’ – is there one?
  • Lines of best fit
  • Confidence and error bars – this practical gives instant error bars, which can then be adjusted depending on the desired confidence level. As the distance decreases, the absolute certainty obviously decreases to, but a few calculations reveal that the percentage certainty stays the same.

I’m considering asking to include this activity in the department’s Year 7 ‘Becoming a Scientist’ scheme of work, where we already introduce some very simple principles of scientific enquiry.

  1. Stuart Farmer said:

    Thanks for providing such a good summary of the workshop. Glad you enjoyed it and hope you use it in your Y7 SoW. I hope you can make it to the next ASE Annual Conference in Reading, Jan 2013, and you can tell me all about it.

  2. Conor said:

    Thanks for the idea, but I’m a little confused (perhaps just stupid) as to how the experiment looks just before you release the marble.
    Is the cup upside down, so the marble roll does the ramp, through the hole in the rim, hits the opposite side of the rim and pushes the cup across the graph paper?
    Or is it something else?

  3. Stuart Farmer said:

    Conor, you have got it, cup is upside down lined up between the end of ruler and on the axis of graph for marble to enter and push along. Graph is marked where furthest edge of cup ends up.

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