Experiences

An astronomic approach to the Newton’s Laws

Paola Falsini

Italy

High Secondary School

Physics

Teaching in class, Laboratory

Direct

Some years ago I started presenting Newton’s laws using the historical context of the astronomic issues about the planetary motion, according the following model:
1. Galileo’s observations through telescope and growing popularity of Copernican hypothesis.
2. Keplero, the research of the Harmony, calculation of the orbit of Mars, the formulation of the 3 laws.
3. What is the reason of the planets motion? The principle of inertia, the necessity of an action for the circular motions, need for an unique explanation for celestial and terrestrial motions.
4. Newton: the concept of acceleration of the circular motions, the dynamic identity between uniform circular motion and uniformly accelerated motion.
5. The concept of the impression of a force, the second law of motion, the concept of the force as interaction and the third law of motion.
6. From the laws of motion of the planets to the law of universal gravitation.
The topic of gravitation is usually dealt with an aside chapter, after the principles of conservation.
With the innovative approach I suggested I tried to involve the history of Physics. There is not the intent to substitute the history to the study of the Physics, but this method aims to recall the key steps that have leaded to the fundamental concepts and laws of the Physics.
Telling the problems that were common at the time of the scientists, this method aims to highlight that those problems are still the same the students face on nowadays and re-actualize the complex, intense, articulate debate that has leaded to their solution.
Thus the learning path becomes full of sense and attractive. I noted that also the hardest concepts (e.g. the vector acceleration) are understood in an easier and more reliable way.
The particularity lays on the fact that there is not the usual transmission of notion from the teacher. The concepts are built together with the students employing experimental activities, laboratorial models (e.g. the conic pendulum introduced by Hooke as a model of the planets around the Sun), software of Astronomy (e.g. to analyse the data about the orbit of Mars, like Keplero did, in order to track trough triangulation its orbit), book reading, group discussions.
The methodological choice is the core element of the innovation: the student becomes proactive constructor of his own knowledge.