We have developed an exciting non-traditional experiment for our introductory physics laboratories to help students to understand the principle of conservation of angular momentum. We used electric toy cars moving along a long rotating rod. As the cars move towards the centre of the rod, the angular velocity of this system increases. Alternatively, when the cars move away from the axis of the rotating rod, the angular velocity of the system decreases. This allows the students to grasp the striking effects of the conservation of the system's angular momentum. The experiment illustrates the physical laws underlying fascinating natural phenomena and processes such as the origin of neutron star rotation, the motion of planets and the reaction of a helicopter body to the rotation of its blades. In addition, the effect of air resistance on the angular velocity is measured and discussed in detail, as it adds a significant component of realism to the experiment. Realism is often ignored in traditional experiments of this kind. Even though the air resistance effect is minor, we tackled it in our experiment and found it too substantial to be ignored. It is very enlightening for the students to see the reality of air resistance and it will help them to develop a critical approach to the idealized pictures often used in physics. Our experiment is simple and can be implemented in any introductory physics laboratory at little cost.
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