A curious one, indeed. Some people who drive cars or bikes hit other cars. In 1999, a friend of mine from Prague and Rutgers, mathematician Petr Čížek, was killed by a truck that they had crashed into while his lively Russian female friend was driving on a seemingly empty road in Minnesota (I didn't go to that expedition, mostly due to the qualifying exams).
The underpass going to the soccer stadium after a fan association named Ultraside gave a permission to itself to paint it. ;-) It used to be prettier than at random moments – the city hall should have hired them to paint the underpass regularly.
People may collide with other people of different occupations and races. The individual I hit an hour ago was a boxer. And it's a race, not an occupation. ;-) Well, I know that the native speakers actually call it a "breed", not a "race", but I will use the word "race" because it's the same concept as the human races, isn't it (well, except that the separation to breeds was mostly bred i.e. man-made), and I am Czech who has never attended any dog races so there is no room for confusions.
I was just leaving an underpass for the pedestrians and bikes near the stadium of FC Viktoria Pilsen, our recently famous but no longer shining soccer club, which you may see on the picture at the top (I was moving to the right side on that picture; the decoration of the underpass is frequently changing). More or less all of Czechia is accessible via Street View on Google Maps (unlike Germans and many other nations, we're in no way oversensitive concerning the privacy on the web), so you may have a look at the exact situation:
Look at the yellow tunnel (Google Maps)Google has made the Street View really helpful in this case. I think that the screenshot above contains a biker located pretty much at the exact position where I experienced the collision. ;-) My bike was leaving the underpass at a relaxing speed, not much above 10 miles per hour.
Suddenly, a dog jumped at me from the right side (and perhaps from the "top"). Along with its owners (or business partners), it was previously playing with a tennis-ball-sized colorful ball that just bounced off a nearby trash can, I was told, which is why the dog's world line became so chaotic. The mammal could have landed on my handlebars for a little while. It's hard to remember every split second in the moment of such a shock but I believe that I hit my brakes within 0.1 seconds.
At any rate, I was flying over my handlebars and landed on the sidewalk. It had to look rather scary. An hour later, it looks like two mild abrasions on the left knee and one more abrasion near the right foot are the only visible negative consequences. Nothing else but my breath was knocked off for a while, much like the bike chain. The owners of the dog were kind enough to offer me some help and return the chain to its prescribed place. I verified that the left knee was just painful but not broken in any measurable way and so on. Even the cell phone seems to work. When my moped collapsed on ice just 150 meters from this place 5 years ago, my digital camera got damaged and its LCD display stopped working in a few days.
A horny cruel monster and a relative of my collision partner
The bastard's weight was 33 kilograms, I was told. (The dog was an alpha male; the correct weight of adult males should be 30-32 kg.) This brown villain apparently wasn't injured at all, despite its hitting an object that is 2-3 times heavier than the dog and fortified with some metallic components. Because kids' speed is much lower, much like their resiliency, I find it plausible that a kid that would jump on a bike in similar states of motion (but with the kid-like speed) could be fine, too.
They seem to be godless killing machines. ;-) Your humble correspondent has just checked that the boxers may achieve the maximum speed up to 35 miles per hour, 2-3 times faster than my bike at that moment. So the total momentum was actually close to zero – the center-of-mass frame may have coincided with the laboratory i.e. sidewalk frame.
I don't know how many boxers – canine or human ones – may be reading this physics blog. But those who are reading this sentence right now are encouraged to slow down whenever you are approaching a corner, e.g. the corner of an underpass. A corner is an L-shaped boundary of matter. You are too dangerous!
Three hours ago, the idea of a traffic accident involving a dog looked bizarre to me. But I turned on TV now and the first thing they showed the viewers was this today's video of an event that took place 3 days ago:
Dogs are apparently organizing Global Days of Traffic Accidents these days. Ms Andie Valerio is said to have saved the life of the dog on the L.A. highway. But my experience today suggests that instead, she has saved the lives of dozens of the drivers while she has preserved the godless killing machine.