swinging a swing -- the solution?
Oct. 30th, 2006 09:19 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
miriam_eI think what the kid on the swing does is pump the swing's motion with gravity, because they are not a closed system after all. They are coupled with the Earth through gravity and the structure of the swing-supports standing on the planet.
It is easiest to understand if you imagine the kid standing on the swing seat (like some kids do).
All the kid needs is a slight asymmetry, then they can let themself be accelerated downward toward the Earth slightly off-center. Because of the curve of the swing's path this gives it a slight kick out from the vertical. Now the kid gently stands again as the swing moves back, and as it starts moving forward they let themself fall downwards again, using the deceleration against the seat to push the swing forward again.
Each time this is done, the movement away from the center is greater so it becomes easier to add more energy to the swing from gravity.
Is this right do you think? It feels right to me.
It is easiest to understand if you imagine the kid standing on the swing seat (like some kids do).
All the kid needs is a slight asymmetry, then they can let themself be accelerated downward toward the Earth slightly off-center. Because of the curve of the swing's path this gives it a slight kick out from the vertical. Now the kid gently stands again as the swing moves back, and as it starts moving forward they let themself fall downwards again, using the deceleration against the seat to push the swing forward again.
Each time this is done, the movement away from the center is greater so it becomes easier to add more energy to the swing from gravity.
Is this right do you think? It feels right to me.