3 ms·
Easy solution is to set a momentum (or kinetic energy?) limit, rather than a speed limit.
by cozzyd 5y ago
Easy solution is to set a momentum (or kinetic energy?) limit, rather than a speed limit.
- tylerfontaine 5y agoSo then a motorcycle could legally go 200mph? And loaded tractor/trailers could go 20MPH? NB: I didn't do the math, so this is probably mildly hyperbolic, but I think it illustrates the point.
- cozzyd 5y agoNo, motorcycle could go 25 MPH. Loaded trailer 2.5 mph. Sounds about right to me for urban areas :)
- jessaustin 5y agoThis proposal makes a lot of sense!
- bifrost 5y agoOr keep people away from cars.
- tzs 5y agoI don't think either momentum or kinetic energy are very good measures here. Consider getting hit in the head with a fastball pitched by a major league baseball pitcher. A baseball weighs ~0.145 kg, and a fastball might be going 45 m/s. That gives a momentum of 6.5 kg m/s, and a kinetic energy of 146.8 J, and a serious possibly life threatening injury. Now consider getting hit by a fully loaded B-52 (220000 kg) being towed at 0.5 m/s. That has a momentum of 110000 kg m/s, and a kinetic energy of 27500 J. That's ~17000 times the momentum of the baseball and ~190 times the kinetic energy, but all it will do is knock you over. (You might subsequently get run over by it, which would do a lot damage, but that injury will be from neither the momentum nor the kinetic energy).
- blacksmythe 5y agoKinetic energy is a good measure for a baseball, because essentially all of the kinetic energy is being transferred from the small object to you. Kinetic energy is not a good measure for a car or B-52, as after the collision the large object has essentially the same kinetic energy, and a very small fraction has been transferred to you. A bicycle is more toward the small object side, as a pedestrian is going to absorb a good fraction of the kinetic energy of the rider, which is much larger than the kinetic energy of the bicycle itself.