A Practical Investigation Task with the Computer at Secondary School: Bridges and Hanging Chains

Almost everywhere you can come across hanging chains and cables. Examples are necklaces, power lines, and cables that support a bridge surface. Do these cables all hang in the same mathematical shape? The first thought of many a pupil will be: this is a parabola, isn't it? In the computer learning environment Coach you can easily measure this on digital images. It will turn out that the parabolic shape quite often occurs with bridges, but that an ordinary chain does not hang as a parabola. Can this be understood? We shall show that a key idea for solving the problem can be discovered by measuring on digital images and that this can be theoretically explained with basic physics. It also leads to a simple computer model of hanging chains. We shall discuss our learning material and classroom experiences, and in this way present an example of how ICT and context situations can contribute to the realisation of challenging cross-disciplinary investigation tasks.