I'm sure this is just a question of not knowing the right search terms, but I'm trying to find out how much energy I would need to put back into a pendulum in order to keep it swinging forever.
Specifically, I'm toying with the idea of building something like one of those automatic swings that rocks a baby but mechanical, rather than electric and possibly large enough for a bigger kid or even an adult. Kind of like a giant grandfather clock with a human pendulum.
I'm sure the amount of push required to keep the swing going indefinitely would be in proportion to the weight of the pendulum (or kid, or lazy grown up) but while I've found dozens of websites with equations describing the period of the pendulum but nothing describing with how much force I need to push to keep it going. Can someone direct me to a resource or suggest different search terms?