AGE RANGES: Key Stage 3 - BAE Systems Education Programme

1 age ranges : Key Stage 3 TASK: The students investigate how engineering is used to improve sports equipment and aid athletes. Students consider aerodynamics and how an objects drag can be reduced. Students then test the aerodynamics of a cycling helmet and record their findings. OBJECTIVES: Students read a worksheet about aerodynamics and drag. They then create an experiment to see where a cycling helmet has the most drag and resistance. National Curriculum Science KS3 Scientific thinking ) Using scientific ideas and models to explain phenomena and developing them creatively to generate and test theories ) Critically analysing and evaluating evidence from observations and experiments Practical and enquiry skills ) Use a range of scientific methods and techniques to develop and test ideas and explanations Energy, electricity and forces ) Forces are interactions between objects and can affect their shape and motion Curriculum opportunities 4c) Use real-life examples as a basis for finding out about science Teachers notes Activity: Introduction Time: 10 min Resources: Teachers notes How many of your students watched the Olympics in 2008?

2 How many students are looking forward to the 2012 Olympics in London? The athletes work incredibly hard to get to the top of their profession and ability. However, are the students aware of the science and engineering used to create the equipment which helps them to achieve these impressive feats? But how much can science really help athletes? Engineering is used to create all kinds of sports equipment from golf balls to faster hulls on sailing ships. Margins for winning are getting tighter and tighter. In Athens 2004, Chris Hoy won his Olympic gold medal for cycling by seconds. The coxless four won in rowing by just - undoubtedly these athletes were helped by their equipment. Activity: Aerodynamics and drag Time: 10 min Resources: Aerodynamics and drag worksheet Teachers notes Explain to the group that they are going to test and then improve on the design of a cycling helmet by considering the effects of aerodynamics and drag . As a group read the Aerodynamics and drag worksheet found at the end of this document.

3 Activity: Preparing for the experiment Time: 25 min Resources: (One per group) Cycling helmets Ball of wool, this should be a contrasting colour to the cycling helmet Double-sided stick tape Teachers notes The students are going to prepare their cycling helmets so they can see how the air flows around them when placed in front of a fan. The test is prepared by: 1. The group is split into teams and each team is given: A cycling helmet, a ball of wool and double-sided sticky tape. 2. The groups then cut approximately 50 short tufts of wool each about 5cm long. 3. The groups cut four strips of double-sided sticky tape (long enough to go over the width of their cycling helmet) 4. The tufts are then placed equal distance from one another on the four pieces of double sided sticky tape (approx cm apart) with the end of the wool trailing off the tape. 5. The four pieces of double sided sticky tape are then placed over the cycling helmet equal distance apart.

4 The tape must be put on cycling helmet from side to side, not front to back. The helmet should now have lots of loose ends of wool facing front to back with the front end stuck down and the back flapping free. When placed in front of a fan the wool will move to indicate the airflow around the cycling helmet. Activity: The experiment Time: 15 min Resources: A fan Wire mesh (optional) A ball (That the cycling helmets can comfortably sit on) Teachers notes Place the fan on a table at the front of the class where the students can observe the experiment. If possible place a wire mesh about 10 cm in front of the fan, this will help the air blow straighter and improve the experiment. Each group takes it in turns to put their cycling helmet on the ball and hold it 30 cm in front of the fan. The wool will move showing how the air passes over the cycling helmet. The students observe the motions of the wool and make detailed notes about its movement. Discuss with the group what they think the wool will do if there is good aerodynamics?

5 What do they think it will do in an area of high drag? Tell the group the visual signs of drag: Tufts that move around chaotically are a sign of drag. Tufts that move in the opposite direction to the airflow are a sign of high drag Tufts that stay in line with the airflow are a sign of lower drag. The students will need their notes for lesson 2 when they will use this data to improve the cycling helmet. What is Aerodynamics? Aerodynamics deals with the motion of gasses (like air) and the forces produced by these gasses on moving or stationary objects. For example aerodynamics affect moving objects like aeroplanes, cars, birds and gliders as well as stationary objects like buildings and bridges. This research into aerodynamics is then used to improve manmade objects. For example cars are modified so they can travel easier and use less petrol, and buildings are designed that can withstand the force of the wind. Aerodynamics also affects athletic performance in many sports as this science is used to improve sports equipment.

6 For example, do you know why golf balls have little dimples on them? Golf balls have dimples because, due to aerodynamics, the dimples modify the drag and lift forces that affect the ball. Which, in practical terms, means a golf ball with dimples on will go twice as far as a perfectly smooth ball? Not a bad bit of sports equipment engineering! Without those dimples, even Tiger Woods would only be able to hit a golf ball half his usual distance. What is drag? Drag is a resistance force to the forward motion of any object, including cars, aeroplanes, runners and sports equipment. If an objects thrust force is greater than the drag force it will move forward. If the drag force is greater it will slow and stop. There are four types of drag: friction drag, form drag, induced drag and wave drag. These four drag forces are created by the shape of the object, the smoothness of the surfaces and the velocity of the object. The two main types of drag we need to consider for our experiment are: Friction drag Friction drag is the drag force created by the friction force on the surfaces of the object.

7 As you know it is easier to push a box over a smooth floor than a thick carpet. This is because the friction force on a thick carpet is greater than a smooth surface. For example, the friction of air passing over the wings of an aeroplane is reduced because aeroplanes are made as smooth as possible. If you look closely at the surface of a wing on a plane you ll see that all the sheets of metal join smoothly and the rivets are rounded over and flush with the surface. Form drag The form drag is directly related to the shape of the object. A smooth, streamlined shape will generate less form drag than a blunted or flat body. You can see this if you put your hand out in the wind. If you hold your hand up facing the wind you ll feel a lot of pressure pushing your hand back. However, if you hold your hand on its side the drag is greatly reduced. These two types of drag are often added together and called the profile drag or parasite drag. We are going to use our knowledge of these two types of drag to test and then improve on a cycling helmet design.

8 A good aerodynamic helmet can reduce the amount of drag a cyclist encounters by approximately 2%; maybe enough to give save seconds?