Pushing in time

How Do You Make a Swing Go Higher?

A swing has one natural rhythm, and small pushes timed to match it add up into a big arc.

Timing beats strength every time.

Step 1 of 5

A swing is a pendulum, and pendulums have one rhythm.

A heavy adult and a small child swing at the very same rate

The time for one back-and-forth depends on the rope length, not on how far it swings or how heavy the rider is.
Step 2 of 5

Energy added in time is kept; out of time is cancelled.

Push with the motion and every push adds. Push against it and the next push undoes the last. Rhythm decides whether effort accumulates.
Step 3 of 5

Pumping changes where your weight sits.

Leaning back and stretching your legs at the bottom, then tucking at the top, moves your body relative to the ropes and does real work.
Step 4 of 5

Each arc only adds a little.

One pump barely helps. Twenty pumps in rhythm build a big arc, which is why getting going takes patience and then feels sudden.
Step 5 of 5

The same trick shows up everywhere.

Push anything at the rate it already wants to move and small pushes go a long way.

A wine glass singing, a bridge swaying and a radio tuning in are all systems that respond hugely to pushes at their own natural rhythm.

Standing up on a swing shortens the effective pendulum, which speeds up the rhythm — pump to the new timing or you will fight it.

The short version

A swing has one natural rhythm, and pumping works by adding a small amount of energy in time with it, arc after arc.

Sit still on a swing and have someone push once every second arc instead of every arc. The build-up nearly stops.