# Exponential Decay of beer foam Design Lab

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Introduction

Exponential Decay of Beer Foam

Physics Design Lab

11/21/2012

Introduction:

The aim of this investigation is to find the decay constant of beer foam. This practical will revolve around the process of decay of beer foam. When a beer is poured into a glass, the gas in the beer begins to form bubbles, also known as a head. This effect will be maximized by not only using warm beer, but by also pouring the beer fast into the glass. For this experiment, the same brand of canned beer will be used. The bubbles also burst randomly similar to the decay of radioactive nuclei, where the rate of decay of bubbles is proportional to the number of bubbles. Resulting in the equation:

Where:

is the decay constant.

t is the time.(seconds)

N is the number of bubbles.

Equation derived:

However when t = 0 and N =

The value of c =

Research Question:

Middle

The image above is a representation of a beer head where the volume could be found. d is the diameter of the cylinder, h is the height of the head, a is the approximate size of the bubble, and L is the length of the cylinder. If the bubbles are of uniform size, then the volume of the head is proportional to the number of bubbles. The beer holder in this experiment will be a measuring cylinder. The cylindrical shape will allow us to relate easily the change in volume with the change in height.

Diagram:

Variables:

Variable Type | Variable(s) | Method of Measuring |

Independent | The time taken for the beer to foam and settle. | The time will be measured in seconds using a timer, to give the foam time to form and build up. |

Dependent | The height of the foam that is formed (the head). | This will be measured using the measuring cylinder scale, by marking relevant points (initial height, maximum height reached) |

Conclusion

Two graphs of linear and exponential will be plotted. The graph will be in the form of y = mx + c allowing to plot a straight line. As a negative symbol means that decay in the beer foam is taking place. Where c is the gradient is equal to the decay constant (

).

This student written piece of work is one of many that can be found in our International Baccalaureate Physics section.

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