Timeline for Is there an optimum length for a swing for a childs mass?
Current License: CC BY-SA 3.0
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| Aug 2, 2018 at 0:04 | comment | added | David White | I don't know how to model it, but there is some kind of "resonance" between the length of the swing and the length and mass of the child's lower legs as he "pumps" the swing. For very long ropes on the swing, it is VERY difficult to pump the swing such that it gains much height. I suspect that very short swings have a problem as well. | |
| Feb 6, 2012 at 19:00 | comment | added | dmckee --- ex-moderator kitten | Well, I suspect that $M_{swing} \gg M_{legs}$ is pretty bad for the efficiency in that meaning. With a child's legs being less than 10 kg, that suggests that swing massing over ~100 kg would be impossible to move much. Of course 100 kg of steel cable makes one heck of a swing. I suspect that air resistance limits the height before we get that long, which makes my answer incomplete. In my defense I assumed you were talking about reasonably realizable swings. The tallest one I've used was about 6 meters, and I was able to get it near horizontal. That was fast. | |
| Feb 6, 2012 at 14:39 | comment | added | user1873 | Yes, because velocity is a function of gravity, longer swings are better. There still must be some maximum length, at which the mass of the child is insignificant to the weight of the rope, chain, seat. At some point, the child would be unable to overcome the inertia of the swing to get it going(and wind resistance). This is kind of what I meant by pump efficiency. A mile high swing that weighed a ton, couldn't begin to get any height using the mass of a child's leg pumps. | |
| Feb 6, 2012 at 3:13 | comment | added | Manishearth | Yeah, the second half would involve a double pendulum type system, except that second pendulum swings abnormally (as in, it does not swing in the manner that a double pendulum does). Ick. | |
| Feb 6, 2012 at 1:59 | history | answered | dmckee --- ex-moderator kitten | CC BY-SA 3.0 |