Quote:
|
Originally Posted by MikeDubreuil
I might have been the first person who wanted to quantify the impact force. However, anyone who said getting hit by a Segway wasn't that bad talked about forces ambiguosly.
|
The main problem with the way you tried to "quantify the impact force" is that you implicitly assumed that the Segway would impart all its momentum in the collision. That would happen only if it was out of control
and lost power at the moment it hit.
Quote:
|
Originally Posted by MikeDubreuil
I welcome anyone who would like to to fix the calculations to do so.
|
Okay. The first thing to realize is that the impact force is (approximately) proportional to the velocity.
Not to the square of the velocity; kinetic energy is not the relevant quantity (unless you want to assume that people are equivalent to brick walls). We want to consider the momentum of the moving rider and Segway,
mv. For the purposes of argument, I'll accept a mass of 200 pounds (yes, pounds are actually a valid measure of mass, and indeed the legal definition of a pound specifies a specific mass, not a specific force) and a velocity of 18 feet per second. Converting to metric is about 90 kg and 5.5 meters per second, for a momentum of slightly less than 500 kg*m/s.
Second, the force depends on the amount of time the Segway is in contact with the person. How does half a second sound? (Note that assuming a longer time decreases the applied force, so I'm being very pessimistic here.)
Finally, the Segway will almost certainly be braking itself during the collision, so a good portion of the total force will be transferred through its wheels to the ground rather than through its frame to the pedestrian. According to the video, it takes less than half a second to come to a full stop, even without running into something. If the Segway is also pushing the pedestrian during the entire time, a simplistic integration shows that more than three fourths of the momentum is dissipated through the wheels, so the momentum transferred to the person can be no more than about 125 kg*m/s. To do that in one half second requires less than 250 Newtons of force, or about 1100 pounds.
Does that sound like a lot? It's not. It's about what you'd get if you rolled out of bed. For comparison, it's only a little more than twice the amount of force the 167-pound rider's feet would absorb if he jumped off the Segway.
Quote:
|
Originally Posted by MikeDubreuil
The problem is that the calculation will never be accepted because then someone will argue that I neglected how the Segway will try to reverse itself.
|
If you do neglect that fact, then your calculation is missing an important -- perhaps the most important -- term.
Quote:
|
Originally Posted by MikeDubreuil
Either way, the force issue is a moot point. The most important point is that the Segway will increase sidewalk collisions.
|
That's not a "point". It's a
claim, for which I have seen no support. Have you ever ridden a Segway for more than a few minutes, Mike? A rider on a Segway is not some juggernaut having a limited ability to accomodate his surroundings. He's not like a bicycle rider who needs to go fast in order to remain stable. He is in many ways just another pedestrian, but with a little higher view and the benefit of increased speed when desired.
Quote:
|
Originally Posted by MikeDubreuil
The bicyclists are lucky to be in a state with bike lanes because if they didn't they'd be driving in the road with normal traffic.
|
Um...I think
mtaman02's comment was complaining that the bike lanes in those states
are in the road next to motor traffic.