3 ms·
Isn't the flaw that the posted model assumes that you're essentially bolted to the swing by your ass, and only able to move your legs and upper body, excluding
by avar 3y ago
Isn't the flaw that the posted model assumes that you're essentially bolted to the swing by your ass, and only able to move your legs and upper body, excluding the arms?
Whereas an actual person on a swing has two points of contact along the pendulum: where they sit, but also the point at where their arms are grabbing the rope (or "rod", in this model).
I think what the GP is talking about is a technique where you essentially perform a partial pull-up near the top of the arch.
- amluto 3y agoI think m_1 is roughly your butt, and m_3 is roughly your shoulders. Phi is the angle your body makes wrt the chain. So pulling on the chain changes phi. I think the idea is that three masses can model a center of mass that may not coincide with the butt as well as moment of inertia — mass, moment of inertia and CM displacement is three parameters, and three point masses gives enough degrees of freedom. But three point masses cannot model non-rigid-body effects. The offset of CM from butt can vary (by bending one’s knees if nothing else), the CM offset from the swing can vary in two dimensions. I don’t know how much this matters.