If you push a child on a playground swing forward one time and let go, the swing will begin to move back and forth, gradually slowing down until it eventually stops.
The Swing's Motion: A Pendulum Analogy
When given a single push, the child and the swing system behave much like a pendulum. A pendulum is an object that swings freely back and forth under the influence of gravity. Initially, the swing reaches a certain height and then swings back through the lowest point to a similar height on the other side before repeating the motion.
As stated in the provided information: "The child and the swing become like a pendulum, swinging back and forth with constantly reduced motion, and depending on the drag level (aerodynamic and bearing) until it stops."
Why the Swing Slows Down
The motion of the swing is not perpetual; it has constantly reduced motion. This means that with each swing back and forth, the maximum height reached decreases, and the speed at the lowest point becomes less. This reduction in motion is caused by resistive forces.
The primary resistive forces mentioned are collectively referred to as the drag level. These include:
- Aerodynamic Drag: This is the resistance caused by the air pushing against the child and the swing as they move through it. Faster movement results in greater air resistance.
- Bearing Drag: This is the friction in the pivot points where the swing chains or ropes attach to the swing frame. Friction converts some of the swing's energy into heat, slowing the motion.
Factors Affecting How Long It Swings
The duration for which the swing continues its motion depends significantly on the drag level. Factors contributing to drag include:
- The weight and shape of the child and swing (affecting aerodynamic drag).
- The efficiency and condition of the swing's bearings or pivots (affecting bearing drag/friction).
- Environmental conditions like wind (though the reference specifically mentions aerodynamic drag from motion).
The Final Outcome
Because of these resistive forces, the swing's energy is gradually dissipated. Each swing is slightly shorter and slower than the last. This continues until the swing no longer has enough energy to overcome the drag forces and gravity, at which point it stops its back-and-forth motion and comes to rest at its lowest point.
