Rate of change of acceleration seems to be rather smooth compared to say any ICE car in launch mode, manual or automatic, in which case you have positive and negative jerk before you reach equilibrium.
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Insane / Ludicrous launches and third row seating
- Thread starter mgboyes
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- Driving Dynamics Model S
Rate of change of acceleration seems to be rather smooth compared to say any ICE car in launch mode, manual or automatic, in which case you have positive and negative jerk before you reach equilibrium.
Yes, and if we ignore the Z-axis as you suggest in each case then when you lie flat on the floor (or stand on your feet) you are in freefall in the XY plane, and when you accelerate inside the car you are not in freefall in the XY plane, hence my point that these are not equivalent.
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
OK I just read this thread.
1. Don't do Ludicrous launches with kids in the 3rd row - it can absoultely cause them harm especially their necks. Like it was said above it's very similar to VERY hard braking if you're facing forward, which generally is not a nice experience.
2. mgboyes is absolutely spot on with his physics. Don't argue him any more, anyone doing so is digging themselves a deeper hole. The feeling you get from your gut on heavy accleration comes from the intestines and nervous plexi in the abdomen being squashed against the posterior wall of the abomen, which is more firmly in contact with the car seat, while the contents of the abdomen actually have some freedom to move relative to the abdominal wall (i.e. they are not completely fixated). The feeling you get from the head is likely caused by both pull on nervous structures which excites them electrically (like when you hit your elbow and get a radiating pain), resulting from the same phenomenon (the brain, spinal cord and spinal nerves all have some degree of freedom of movement due to them being suspended in the cerebrospinal fluid space). Another thing that I believe causes the symptoms experienced is a brief relative ischemia (not enough oxygen getting throug) and fall in blood pressure due to the fact that blood in vessels is a freely flowing fluid which accelerates a bit later than the vessel walls.
The key word here is INERTIA. Different parts of the body have different degrees of intertia relative to eachother, due to anatomic arrangement, density, fluidity and so on. The stronger the accleration force is the larger the difference (delta) will be in absolute terms between these different parts with different degrees of inertia.
1. Don't do Ludicrous launches with kids in the 3rd row - it can absoultely cause them harm especially their necks. Like it was said above it's very similar to VERY hard braking if you're facing forward, which generally is not a nice experience.
2. mgboyes is absolutely spot on with his physics. Don't argue him any more, anyone doing so is digging themselves a deeper hole. The feeling you get from your gut on heavy accleration comes from the intestines and nervous plexi in the abdomen being squashed against the posterior wall of the abomen, which is more firmly in contact with the car seat, while the contents of the abdomen actually have some freedom to move relative to the abdominal wall (i.e. they are not completely fixated). The feeling you get from the head is likely caused by both pull on nervous structures which excites them electrically (like when you hit your elbow and get a radiating pain), resulting from the same phenomenon (the brain, spinal cord and spinal nerves all have some degree of freedom of movement due to them being suspended in the cerebrospinal fluid space). Another thing that I believe causes the symptoms experienced is a brief relative ischemia (not enough oxygen getting throug) and fall in blood pressure due to the fact that blood in vessels is a freely flowing fluid which accelerates a bit later than the vessel walls.
The key word here is INERTIA. Different parts of the body have different degrees of intertia relative to eachother, due to anatomic arrangement, density, fluidity and so on. The stronger the accleration force is the larger the difference (delta) will be in absolute terms between these different parts with different degrees of inertia.
Yeah holy crap, done arguing... This thread reminds me being told women can't drive because their ovaries will fall out. No rational counter-argument will be convincing.
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I have the perfect solution to keep your kids safe.
Spoilsport
In all seriousness though, the point about 1g acceleration in a rear-facing seat being indistinguishable from 1g braking in a front-facing seat is a great one.
And it also just occurred to me that my kids (4 and 6) have been on rollercoasters that pull ~2.5g (though I'm guessing this was in the vertical direction relative to their bodies, i.e. going around high speed curves, rather than horizontal acceleration) - again clearly this worked out fine, and has been signed off by all manner of health and safety folks with clipboards.
Still... I'll suggest that my wife sticks to sport mode for the school run!
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