3 ms·
Jerk is also very important for road or rail track design. If you imagine needing to make a 90 degree bend, the "obvious" way to do it is by rounding off the co
by wlesieutre 2y ago
Jerk is also very important for road or rail track design. If you imagine needing to make a 90 degree bend, the "obvious" way to do it is by rounding off the corner with a circular radius.
But if you do that, it means the vehicle goes from having 0 sideways acceleration to experiencing 100% of the centripetal acceleration to move an object on a circular path (a = v^2 / r) instantaneously.
As an occupant of the car, that means you go from sitting comfortably to suddenly being thrown sideways.
It's much more comfortable if you ease into the turn, with the track design considering the rate of change of acceleration. If the designer didn't consider jerk you would definitely notice.
- matsemann 2y agoThat's why loops on roller coasters aren't perfect circles as well then, I guess?
- wlesieutre 2y agoThe forces you experience in a loop must be a bit more complicated because the turning forces in a car are perpendicular to gravity and in a loop are sometimes in-line, but yeah I would think that's why the entry and exit are a softer curve.
- majormajor 2y agoYeah, the more circular ones are pretty intense - https://guidetosfot.com/rides/shockwave/ https://guidetosfot.com/rides/shockwave/
- rcxdude 2y agoIn part, maybe. The bigger reason is the roller coaster slows down near the top of the loop, so even for an constant vertical acceleration you need a non-circular shape.
- matsemann 2y agoYeah, but I was just thinking that the sudden curve would jank your head quite a bit, compared to easing into it.
- malfmalf 2y agoThe curve that is used is a Clothoid: https://en.wikipedia.org/wiki/Euler_spiral https://en.wikipedia.org/wiki/Euler_spiral Usually for any curve you go straight-clothoid-arc-clothoid-straight For trajectory AND for pitch and roll
- wlesieutre 2y agoNeat!
- antod 2y agoBack when I studied highway engineering they called it spiral-circle-spiral, and the vertical curves were more parabolic. The methods for laying them out were very low tech aimed at drafters and on site contractors rather than mathematicians. I can't remember the layout methods though.