It is an apparatus with magnetic levitation which makes it possible to reproduce in class the movements of space. Indeed, a magnet of néodymium in the shape of flying saucer is maintained in the air, by a solenoid whose magnetic field is controlled at every moment by an infra-red ray. 

By making turn this magnet into blowing in a straw, one can illustrate the principle of inertia in a brilliant way since that a suspended object can turn up to one hour before stopping.

The stop watch with reflexion fills this role. **time-out** the apparatus be used to measure the time of passage of a carriage above of a narrow tape as blank paper blanc pose on a table black. It is started when it passes above the paper which acts like reflectors.

This light self-contained equipment sets at a carriage using a tape of the type " velcro ". It comprises a cell of starting and stop with infra-red placed on its lower part. One obtains a reading having a precision of thousandths of second. Acceleration can be provided by an elastic tape or by using a tilted plan.

This system with infra-red raies comprises a transmitting module and a receiving module laid out one opposite the other. The transmitting module sends two infra-red raies which are intercepted by the two detectors of the receiving module. The interruption of the first ray puts the stop watch goes from there while the interruption of the second ray stops it. The stop watch located on the receiving module measures the time of passage between the two rays with a precision of thousandths of second. It is easy then to deduce speed and acceleration.

The system does not include/understand any connection of wire and the distance of approximately 20 cm between the rays is fixed. This simplification helps the pupils with better visualizing the principle of the instantaneous velocity measurement