TOBOGGANING
It wouldn’t be right to end our discussion of trajectory optimization without discussing
the famous Brachistochrone problem. We do it here in this last section in the context of
designing a slide which will get the rider from the beginning to the end in the shortest
amount of time.
We assume in this study that the slide will be constructed out of frictionless material. We
let x denote, as usual, horizontal displacement and we let y denote vertical displacement.
In contrast with earlier conventions, we assume that y increases as one moves downward.
The slide will connect two points having coordinates (x0, y0) = (0, 0) and (xf , yf ). The
toboggan starts from rest at the top of the slide. Hence, initially the toboggan has zero
kinetic energy and zero potential energy (due to gravity). Since the slide is frictionless,
there is no loss of energy as heat. By conservation of energy, the total energy must always
remain zero. So, when the toboggan has dropped to level y,