A Slowly Rotating Coordinate System
Find a merry-go-round for sale (or a rotating panorama tower or any other slowly rotating system). A cuddly toy on a string is a useful multi-purpose piece of equipment for experiments in the park. In this experiment, the toy is used as a pendulum. Set it in motion, hold your hand still and observe.
"It made a star, it made a star." An exalted 9-year old tells his teacher and his friends and anyone who will listen. He draws the figure with his hand. Many children, in fact, do observe, and those who do are happy to share and discuss their observations - others just let the animal swing and look everywhere else.
The hot-selling miniature pendulum is a striking experiment, even more so for more slowly rotating systems. It is usually appreciated by the older students, but can small children really learn anything from it? In December 2001, a class of 10-year olds visited the park, doing a number of experiments, starting with this one, using their own toys, so they knew that no-one had cheated. One of the teachers brought up the question why we would do this, so the question how we can know that the Earth rotates was discussed. The visit took place just before Christmas, and the class teacher had no time to follow up on their experiences. Three months later, we visited the class and interviewed the children. Many of them recalled the pendulum in the carousel, and also that it had something to do with the rotation of the earth, commenting e.g.:
"In the Pony Carousel, the cuddly toys on the strings started to move like this. I think it was to prove that the Earth is rotating."
"I learned that when going in the Pony Carousel, the cuddly toy kept going in the same direction while I was going around."
How does a teacher move on from here to make use of the children's observations, which also involves taking different systems for reference. One possibility is to find a carousel on a local playground and try it with e.g. a water pistol or throwing balls to a friend. A difficulty may be that safety regulations seem to make carousels on playground few and far between. A more serious concern, however, is that the teacher may not share the children's excitement. Russell Stannard /4/, who interviewed several scientists observes that "An essential ingredient for appreciating science is the sense of wonder. ... I am struck by the marked change that come over young people as they enter their early teens. Too often an air of bored indifference sets in and the precious sense of wonder is to a large sense lost, never to be regained. ... The scientists I have spoken to still possess it".
We have found that adults without physics training often have difficulties with this experiment. If they remember anything about inertial forces, it is certainly not the Coriolis force. Instead of letting the object swing, they typically let it hang still and wait for the centrifugal force to make it hang to the side. However, the centrifugal force is not very eye-catching in slowly rotating coordinate systems. Visual studies of horizontal acceleration is more rewarding in other rides, e.g. in the wave swinger discussed in the next section.
Doing unknown experiments with unfamiliar equipment in exciting rides in an unknown park is very unlikely to lead to any physics learning. If there is a park close-by that children are likely to have visited before, that is the obvious choice. Find out if the park arranges special days or hours for experiments (such as the Physics Day in Adventure World, described by Shelley Yeo /6/). If not, find out suitable days and times from the park when the queues are likely to be short. Divide the class in smaller groups that focus on experiments in two or three rides and present their findings to the rest of the class after the visit. Use the park's www-site to find information about the rides and plan what experiments to perform and what equipment to use. Do not forget safety considerations, and if in doubt about the equipment, consult the park before the visit. Let the class try the equipment in a more quiet condition, such as a local playground /7/. Remember that the more exciting rides may require a number of tours before the pupil can concentrate on observation of the equipment. Those tours may be seen as occasions when the body is used as a measuring device and the experience, discussed before the next tour in the same ride. To find out more about "the forces behind the fun", visit Annenberg/CPB's site about "Amusement Park Physics" /8/. If the students are familiar with CBL equipment, it should obviously be used in the park, as described e.g. Ref /9/.
The preparations are essential. Without them, the originally intended use of an amusement park is too tempting for the students to be able to concentrate on the physics. Physics is fun - but it is also important to help the students discover that "the fun is physics".
