Pumping on a Swing

Effects of Visual Information and Task Constraints on Intersegmental Coordination in Playground Swinging

“…A classic example of such a task is rhythmic movement around a single pivot point: playground swinging. That task is quite similar to the extensively investigated physical pendulum and can be studied in two dimensions with little loss of information, because all body segments are essentially confined to planar motion (Gore, 1970Tea & Falk, 1968Walker, 1989). To achieve successful energy insertion, actors need to adjust the niovements of their body parts to the physical constraints of the swing.…”

Pumping a Playground Swing

“…The largest energy gain is achieved when the swing moves through its lowest position: at this position the rise in CM and thus the increase in angular momentum is maximal. Assuming extensive movement of the swinger along the radial axis, several authors (e.g., Burns, 1970;Curry, 1976;Tea & Falk, 1968;Walker, 1989) have suggested that this method of energy insertion would be observed in a standing swinger.…”

“…Swinging on a playground swing has been studied extensively as a biological example of the well-known physical pendulum (Burns, 1970;Case, 1996;Case & Swanson, 1990;Curry, 1976;Gore, 1970;McMullan, 1972;Simon & Riesz, 1979;Tea & Falk, 1968;Walker, 1989). The initiation of the swinging motion and the angular displacement of the swing are realized by the swinger pumping energy into the swing-swinger pendulum by means of bodily movements.…”

“…The first, called parametric pumping, consists of alternately raising and lowering the swinger's center of mass (CM) along the swing's radial axis (see Figure 1A). This method of energy insertion has been studied by modeling the swing-swinger system as a point mass at the end of a rope whose length is varied periodically, amounting to a parametric oscillation (Burns, 1970;Curry, 1976;Tea & Falk, 1968). If the sum of the external moments is small, the angular momentum is nearly constant: raising the CM yields a decrease in the moment of inertia I (with respect to the suspension point) and thus a proportional increase in the angular velocity  φ and therefore the kinetic energy E I kin =  φ 2 2 of the swing.…”

Time-optimal control of a swing

“…Tea and Falk (1968) show how the elementary concepts of angular momentum and work-energy can be used to explain why the amplitude of a swing increases when it is pumped. Burns (1969) has shown how the problem exhibits a resonance like phenomenon and Wirkus, Ruina and Rand (1998) compare the two different pumping strategies: When the rider is standing, and when the rider is seated.…”