A cart moves with nearly constant velocity and the very low friction air track.
Persistence of motion (constant velocity) when no external forces act on system.
NCEA & Science Curriculum
SCI 1.1, PHYS 2.4
Set cart in motion and observe. Note that the cart must be balanced. If an extra mass is placed at one end of the cart then the cart will sit on the track at an angle. This can cause a quite noticeable net force on the cart, accelerating it with the heavy end forward as the angled cart forces air backward. In this picture a fan has been added to the right end of the cart and a balancing mass has been added to the back end of the cart. The fan was not running in this demo but was used for Newton’s Second Law on an Airtrack.
Individual teachers are responsible for safety in their own classes. Even familiar demonstrations should be practised and safety-checked by individual teachers before they are used in a classroom.
See Newton II demo on air track.
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