Half life of the head on a beer

After the half life of chocolates triumph last October, today we measured the half life of the head on a beer. I'll never get a job behind a bar...

 We measured the height of the froth every 20 seconds.

We plotted Ln(height/mm) against time. I've edited the results for the first 200 seconds because the results deviated from a straight line after that time. So the decay is exponential only at first.

We showed that the gradient is -decay constant. Half life = Ln2/decay constant, which gave a value of 150 seconds. Other results were around 120 seconds.