Just got back from a workshop in Berlin where I met as always an enthusiastic bunch of teachers. On the plane I was flicking through the in flight magazine and found an interesting article on a new safety device for skiers called a snowpulse. It's a backpack that you inflate if you get in an avalanche and involves some interesting physics. The photo shows it inflated, you don't ski with it like that but if you get in an avalanche you pull a handle at it inflates. The gas cylinder doesn't hold enough air to inflate it but there is a valve that uses the venturi effect to draw air in from the atmosphere. Once inflated it not only protects the skiers head but also makes them float to the surface. The explanation in the magazine as that it dos this by increasing the mass of the skier. I thought it interesting that they got the bit about the venturi effect right but messed up the simple physics. This is common when students write extended essays, anything complicated is simply paraphrased but when trying to use their own knowledge to explain something they sometimes get it a bit wrong. I had a look at the snowpulse website where the explanation is that "the airbag raises the victim`s volume and decreases its density, it therefore increases its “floating” capacity in the avalanche." This sounds much more reasonable. The website also has some gnarly videos of people getting avalanched.