Forensics - car and pedestrian

  • Thread starter Thread starter Fred_tuber
  • Start date Start date
  • Tags Tags
    Car
AI Thread Summary
The discussion centers on analyzing a serious pedestrian accident captured in two black-and-white photographs. Participants are focused on estimating the speed of the car that struck the pedestrian and assessing the likelihood of the pedestrian's survival based on the impact dynamics. They explore various methods for calculating the car's speed, including analyzing the distance traveled by the vehicle in relation to the pedestrian's reaction time and stride. The discussion highlights the importance of interpreting data printed on the photographs, with suggestions to investigate the date of the accident for additional context. Participants also consider the physical effects of the collision, noting that the pedestrian likely sustained significant head injuries and possibly abdominal trauma. The analysis includes examining the vehicle's specifications, specifically a Mercedes Benz C-class wagon, to better understand the impact force. Overall, the conversation emphasizes a forensic approach to understanding the accident's mechanics and potential outcomes for the pedestrian.
Fred_tuber
Messages
2
Reaction score
0
I was recently forwarded a link that shows two black&white pictures of an horrible accident - a pedestrian getting thrown in the air by a car. You can click on the link (bottom of message, below), to see the pictures.

Note: although the image is not gorey, it may be disturbing to some. Please exercise discretion before clicking the link.

So, my question is one of forensics: how fast was the car going when the driver blew through the red light, and what is the likelihood that the pedestrian survived?

As far as change in time goes, I cannot interpret the numbers across the top of the photograph. As best I can make out, the offending vehicle traveled from the first set of dotted lines to the third set of lines (thus giving change in distance), which corresponds with the time it took for the pedestrian on the far left to partially complete her step and recoil aghast, which may correspond with the position of the windshield wiper blade on the offending vehicle. This may not be an accurate presumption b/c the victim may have grabbed on to the wiper blade; also, none of the other cars have their wipers on (which does not preclude that our less-than-observant offender could have had the wiper on). Either an appraisal of the human stride and reaction time and/or the average speed of 1/2 cycle of a Mercedes Benz wiper blade would provide an estimate of the time...right?

It looks like the car hit the pedestrian such that his left leg completely buckled and continued to apply force at an angle such that he "glanced off" the hood, hitting his head as the car continued to pass. What would be the force of impact on his head? Did his abdomen suffer trauma, too?

How would we analyze this to assess the pedestrian's outcome?

-F.

Again: although the image is not gorey, it may be disturbing to some. Please exercise discretion before clicking the link. http://poetry.rotten.com/redlight/
 
Physics news on Phys.org
I think the vehicle is a Mercedes Benz C-class wagon, with a curb weight ~3400 lbs.
 
To any of the crude (but clever) ways of estimating time lapse you suggested, I would affix a 'give or take a factor of 2'--meaning that if you estimate the car was moving 20 mph, I would say that the actual value was between 10 and 40mph--not very useful in determining whether the pedestrian could have survived.

I think the best way of obtaining time lapse would be to investigate further the meaning of the data printed across the top of the photo. Are any of the figures a time stamp? (If so, then why not include them along with hour and minute on the far left?)

The other thing you could do is google the date of the accident (June 26, 2002) and look for news items from Western Europe or possibly South Africa. (The date format, the spelling of 'Foto', and the lack of SUV's all say 'not North America'; the fact that everyone in the photo is white-skinned pretty much rules out most of Africa and Asia. Are those white bands on the fronts and backs of the cars license plates or the equivalent? The cars, manner of dress, and condition of the roads point to a fairly affluent society--much more likely to be in Germany or Switzerland than the Ukraine or Croatia.

P
 
It looks to me like the victim rotated a 3/4-turn. The legs were hit first, and in the second frame are pointing to the direction the vehicle came from. so the head and shoulders must have hit near the windshield base and probably jarred the wiper loose. There's no way the victim would have had time to grab anything.
 
came across this by googling; was posted on a local car forum and i wanted to see if there were any news reports.

to wit:

determining the average speed is trivial.

the merc has a known length, so one can determine distance traveled by the benz by measuring the pic by drawing lines and comparing length (in pixels) in powerpoint.

second, the time passed is 6.66 s - 5.85 s from the info in the pics.

from the spider-webbing of the windshield, the guy sustained a decent head injury, at a minimum.
 
Hi there, im studying nanoscience at the university in Basel. Today I looked at the topic of intertial and non-inertial reference frames and the existence of fictitious forces. I understand that you call forces real in physics if they appear in interplay. Meaning that a force is real when there is the "actio" partner to the "reactio" partner. If this condition is not satisfied the force is not real. I also understand that if you specifically look at non-inertial reference frames you can...
I have recently been really interested in the derivation of Hamiltons Principle. On my research I found that with the term ##m \cdot \frac{d}{dt} (\frac{dr}{dt} \cdot \delta r) = 0## (1) one may derivate ##\delta \int (T - V) dt = 0## (2). The derivation itself I understood quiet good, but what I don't understand is where the equation (1) came from, because in my research it was just given and not derived from anywhere. Does anybody know where (1) comes from or why from it the...

Similar threads

Replies
3
Views
2K
Replies
2
Views
3K
Replies
65
Views
10K
Replies
2
Views
502K
Replies
1
Views
4K
Back
Top