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Force, Kinetic Energy, etc. re: Auto Accident

B

beyondaurora

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So...I was in a major car accident two weeks ago of which I am still recovering. The California Highway Patrol officer is trying to piece together the accident and determine fault. I am hoping that some T types (and others) with knowledge of physics and how kinetic energy and all that good stuff works can help me to understand the situation.

I was the passenger in a car driving eastward at approximately 35 mph through an intersection.

The driver of the other car (traveling northerly) states that he had just begun going through his green light at about 5 mph when he collided with my car.

My car sustained major damage (a $25,000 2010 car considered a total loss by my insurance) to my (the passenger) side doors and front wheel area. The door is bent inward, and the other car's license plate is stuck in between the hinging part of the door that connects it with the front end.

The other driver states that his car sustained damage only to his left front bumper.

The CHP officer states that this is all possible because of "transference", that we were driving faster than the other car and therefore when he hit us, it caused us more damage.

This makes no sense to me. If anything, wouldn't our force be transferred to the other guy's car? Plus, how could only his front left bumper be damaged if his license plate is stuck in my car!? (The latter question is rhetorical...the guy is obviously misstating his damage).

In my mind, I cannot see how the other driver could have possibly been driving 5 mph considering the damage to the car (and me...I sustained a concussion, sprained ankle, and severely bruised knees)! If anything, it seems that he would have been driving over the posted speed limit of 25 mph.

What do you guys think? How does this work?
 
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INTJ123

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if you got T boned in an intersection then one of you was running a red light, so it comes down to who was running the red, doesn't matter how fast either of you were going if you run a red then you are just stupid.
 

runvardh

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Yeah, who had the red light? Speed, in this case, only determines if additional charges need to be given out.
 

ygolo

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Sorry to hear about your accident, Beyond. I hope you are recovering well.

To answer your questions, it really depends on the details of the accident and the damage.

What the CHP officer told you is possible if the damage to you car was much wider than it was deep. i.e. more "scrape" than crush.

The scenario that could yield the results that the other driver and the CHP officer is as follows:
Your car scrapes against a near stationary car as it goes by, and the slow car spins/rotates somewhat to take up the impulse of the collision.

Also note that bumpers are made to be sturdier in an impact than side panels and doors.

Again, it depends on the details. Did you get hurt from the car being crushed onto you, or did you get hurt because of the sudden change in direction, and banging up against the inside of the car?

Did the license plate get fused to the side of the door like you got rammed hard, or was it more like the license plate got caught from the side and was peeled off?

These things would be an indication of how "elastic" the collision was. The more elastic the collision the more the 5MPH scenario is plausible. Again, indicates more of a scraping than a crushing.
 
B

beyondaurora

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Thanks for the replies. My question is not that of who ran the red light -- at this point I have no way of knowing that as the driver of my car and the other driver both state that they had the green, and there are no witnesses. (I was looking down when the accident occurred.)

I am trying to understand if and how a car that is going 5 mph can strike a car that is going 35 mph yet sustain minimal damage while the 35 mph car sustains major, irreparable damage.
 

Ivy

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I'm the opposite of a physics expert but it doesn't make any sense to me, either. I'm glad you're recovering and I hope the outcome is palatable.
 
B

beyondaurora

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Ygolo! I can always count on you. You pose some interesting questions. Especially with regard to the license plate. I will post a few pictures shortly for discussion. Thank you!
 

JocktheMotie

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Yep, pictures would help. Like Ygolo said, if it was more of a "scrape" than a crush, then the car being scraped would look far worse. Basically what would happen is that 1 point [point being used here loosely] on the 5 mph car would absorb most of the impact, while the 35 mph car is impacted in a large area by that one point of contact. Similar to the Titanic hitting the iceberg.
 

Feops

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Yep, pictures would help. Like Ygolo said, if it was more of a "scrape" than a crush, then the car being scraped would look far worse. Basically what would happen is that 1 point [point being used here loosely] on the 5 mph car would absorb most of the impact, while the 35 mph car is impacted in a large area by that one point of contact. Similar to the Titanic hitting the iceberg.

This makes sense to me. If you, moving faster, turned his car aside some, then that car would only have a small surface area which then scrapes across your entire side as you carry through. The bumper corner would attempt to crumple inward, but the point of a triangle-like shape would resist folding inward, while you on the other hand had a flat panel with a point being punched in and dragged across it.
 
B

beyondaurora

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http://i163.photobucket.com/albums/t300/beyondaurora/IMG00163-20090929-1654-1.jpg

http://i163.photobucket.com/albums/t300/beyondaurora/IMG00138-20090929-1630.jpg

(Sorry in advance if these links aren't clickable...my browser is a BlackBerry.)

You can see that the license plate sticks into the front of the door jam but does not 'peel' as one would expect in Ygolo's example. Again, my car was driving eastward while the other car was driving northerly. One would expect that the plate would peel in such a way that the license plate nearly faces outward from my door. Instead, the plate mostly continues to face my door as one would expect in the crush example.

Interestingly, the photos seem to show a combination of both a crush and a scrape.

Thanks for the link, Ygolo, for accident reconstruction services. Hopefully the officer will write a favorable report so that I don't need to use such a service.
 

Skyward

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http://i163.photobucket.com/albums/t300/beyondaurora/IMG00163-20090929-1654-1.jpg

http://i163.photobucket.com/albums/t300/beyondaurora/IMG00138-20090929-1630.jpg

(Sorry in advance if these links aren't clickable...my browser is a BlackBerry.)

You can see that the license plate sticks into the front of the door jam but does not 'peel' as one would expect in Ygolo's example. Again, my car was driving eastward while the other car was driving northerly. One would expect that the plate would peel in such a way that the license plate nearly faces outward from my door. Instead, the plate mostly continues to face my door as one would expect in the crush example.

Interestingly, the photos seem to show a combination of both a crush and a scrape.

Thanks for the link, Ygolo, for accident reconstruction services. Hopefully the officer will write a favorable report so that I don't need to use such a service.

You snapped the liscence plate off, so it wasnt really a 'peel,' sure. The hit definitely looks like a scrape since its so wide.

Really, now all that matters is who was running the red light. It could go either way since he could have hit the breaks to screech to 5ish MPH or he was just speeding up when the driver of your car ran their red light.
 

ygolo

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What type of vehicle was the other one, a big SUV? Where was the license place on that car?

I am no expert, but it's hard to see how that amount of damage could be done on one car and not damage the other car beyond just the left bumper. Did you get a glimpse of the damage on the other car? or were you out?

I suppose it is still possible, I don't know of any way to compare damage to other that of other low-speed collisions. The pictures of side collisions were all very severe, but also at much higher speeds.

The door part of it seems like a scrape, but the damage around the wheel, and the hood seems much more severe than what 5 MPH could do. But the I was still thinking of it as a 90 degree angle collision. It is possible the angle was slightly off.

It's the placement of the license plate that really has me the most confused. How could it end up stuck in the car with its sides folded backward and the numbers facing inside? and so close to the mirror?

To me, what makes the most sense is:
  1. First the cars smashed together (where exactly depends on where the license plate was on the other car).
  2. Next the other car bounced back a little and rotated a little.
  3. Then Finally the rotated car scraped in your door panel.

But again, I am no expert.

----
Whatever the physics of the accident, there is another part of the story that bugs me. The other driver said that he was only going through the light at 5MPH.

Why was he going so slow?

Did he claim he stepped on the brakes to slow down to try not to hit your car?

Was he accelerating from a stopped or slowed down position upon the light turning green? If so, what sort of person accelerates even when there is a car in front of him?

Or was he just going 5 MPH in a 25 MPH zone? Who does that?

I suppose he could have been accelerating really slowly though the intersection when you car came through the intersection, and that your car got to the spot first because of the higher speed.

IDK. I am biased. I hope you recover well, and that the driver of the other car is at fault.
 
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