Problem – how can we predict the behaviour of forest fires? Objective and outcomes will appear here – at the moment I don’t want you to see them! Problem – how can we predict the behaviour of forest fires?

Deliberately set fire to some forests in order to study it? Objective and outcomes will appear here – at the moment I don’t want you to see them! Observe forest fires closely (although it might be difficult to be there when they start) Deliberately set fire to some forests in order to study it? Another way?

Chapter 10 Modelling Decay

Each nucleus (dice) has a fixed probability of decaying (1 in 6) Dice experiment. Model: Each nucleus (dice) has a fixed probability of decaying (1 in 6) Each decayed nucleus will stay decayed. Dice roll number dice left remaining

Your tasks…. PLOT A GRAPH OF YOUR EXPERIMENT RESULTS USING THE ‘NUMBER OF ROLLS’ AS TIME. ONE ROLL = ONE MINUTE Then work through each of the following…. Grade Outcome Task E I can work out half lives using a decay graph Calculate the half life for your experiment C I use constant half life as a proof of an exponential relationship Find three half lives for your experiment. Are they constant? What does this tell us about this relationship. A I can explain how an exponential pattern arises Do (C) above then attempt to explain what an exponential relationship is and how the conditions in the experiment gave rise to this relationship

What factor affects what is changing What is an exponential relationship? You get an exponential when the rate of change depends on how much you’ve got Examples: Radioactivity (Capacitors – more on this in a couple of lessons time) Water leaking out of a bucket Air coming out of a tyre Businesses expanding Population explosion For each one: What is changing What factor affects what is changing

Can we explain the exponential shape from the experiment we did?

Testing for exponentials. Constant half life. 2) Constant ratio test.

What is the half life? Is the half life constant? What would happen to the shape of the graph if the half life was longer? How does the probability of a nucleus decaying affect half life?

Plenary 1 Peer Mark Feed back