It’s the end of term and the pupils are expecting "fun" (despite you trying to convince them that all science lessons are fun, of course). In desperation, you think about holding a paper aeroplane competition. This is actually brilliant because it offers plenty of science to talk about. But what if you could build this into a longer-term activity and incorporate the concepts of density and air pressure at the same time?
Instead of density just being about measuring the density of some blocks, and pressure just being about measuring the pressure of your feet on the floor, you can now also bring in the science of flight to these topics. Treated simply, this teaching is perfectly within the grasp of key stage 3 pupils, and can also be used in more detail with GCSE classes.
Red Bull Stratos gives you wings…
A great initial hook might be to talk about Felix Baumgartner’s jump from the stratosphere as part of the Red Bull Stratos project. In 2012, assisted by a team of scientific experts, this Austrian skydiver set a world record when he jumped an estimated 39km to Earth from a helium balloon. The Red Bull Stratos website has plenty of information on the science and the story of the jump, or you could simply start with a video clip of the event itself.
There is so much to discuss here. First, there is the question of how the balloon got off the ground in the first place. To help explain concepts such as this, the Airbus Foundation Discovery Space has created a series of videos on the basics of flight, including one on why balloons float.
Going back to Baumgartner’s jump, as the helium balloon initially left Earth’s surface, it seemed fairly empty – encourage pupils to think about what happened to the atmospheric pressure on the outside of the balloon as it rose. Once they have grasped how atmospheric pressure works on a balloon, ask them to think about why Baumgartner had to wear a pressure suit.
In fact, this could lead to the tale of Joe Kittinger, the man whose record Baumgartner broke with his jump and the Austrian’s mentor. During a similar jump the pressure seal on one of Kittinger’s gloves failed and his hand began to swell; he didn’t tell mission control as there was only one way back down at that stage anyway. Thankfully he had no lasting injuries.
Another potential discussion could be about what happens to a helium balloon when you let go and lose it: does it end up in space? In fact, it is likely to burst once there is a significant air pressure drop outside owing to the cold and/or lower density of the air higher up in the atmosphere. This could, in turn, link to extended learning on the sustainability of using helium.
Physics: Bodies in flight
But the learning doesn’t stop there. The Baumgartner jump can also lead into a discussion about how to control the direction of objects in flight. Another of the Airbus videos is helpful here, as it explains how small movements in a helicopter’s rotor blades can change the way the vehicle moves.
In the same way as a helicopter pilot uses rotor blades to control the direction of travel, Baumgartner had to control his own movement through the air when he jumped – if he had gone into a spin, it could have been dangerous as he could easily have been knocked unconscious. Much of his training centred around preparing for this eventuality; he spent a long time in air chambers practising how to move his arms in order to pull out of a spin. On the day, all the training paid off: Baumgartner did begin to go into a spin but was able to avert it without incident.
Paper planes as a lesson activity
A good way to extend the discussion at this point would be to discuss the Bernoulli Effect, which states that as the velocity of fluid flow (whether of air or water) increases, the pressure exerted by that fluid decreases. Perhaps now would be a good time to start showing the pupils how to design the optimum paper aeroplane, too.
The wings of an aeroplane are designed to have fast-moving air above them, which corresponds to a lower pressure, and slow-moving air beneath them to produce the lift. High pressure below and low pressure above means there is a resultant force upwards. You could link this to everyday experiences, perhaps by discussing why it is important to stand behind the yellow line on the edge of train platforms. You want to avoid your coat or bag getting caught on a passing train, of course, but you should also stand back because a fast-moving train will have fast-flowing air around it. Therefore, with slow-moving, high-pressure air behind them and fast-moving air in front of them, a person on the platform will be forced towards the train. This could obviously be very dangerous.
Furthermore, as a nice extension of the concept of air pressure, you can discuss the sonic boom that Baumgartner created when he broke the sound barrier.
Aeronautical engineering is a very popular option with sixth-formers applying to university, so engaging pupils at an early stage with this field is likely to help motivate them in experimenting with the design of things such as paper aeroplanes, as well as the theories of physics that drive these designs. It is hard to find a more engaging real-world example of the use of these principles.
Stephanie Grant is a physics teacher and assistant director of studies at Norwich School