Conservation of linear momentum is well understood and often demonstrated to students. Equally important is the conservation of angular momentum. It is not easy to do meaningful experiments on this, but a highly visual demonstration of almost dramatic impact is the effect of reducing the radius of a rotating mass.
This is often seen in an ice skater performing a pirouette. First they spin round on an axis corresponding to their body, arms outstretched. When they raise their arms above their head, the increase in spin in considerable. Rather than go to an ice rink, students can perform this experiments in the laboratory using the HFC25.
A bench mounted vertical board has a bearing mounted rotating arm along which two weights can be moved by a pull cord operated by the student or demonstrator.
The weights are moved to the outer ends of their travel, away from the centre of rotation. The arm is then spun rapidly by hand, and the weights pulled towards the centre by the cord.
The resulting increase in angular velocity is considerable.