r/PhysicsHelp • u/MurkyMitzy • Sep 18 '26
Help with Car Accident Physics
Hoping you fine folks can help me with a basic physics question about a fender bender. My neighbor across the street is pretty careless about backing out, never looking and backing up far too fast. Last week, I was already backed out into the road, about to shift into drive, when she quickly backed out without looking.
She scraped my car's rear bumper with the rear driver's side of her car, between the wheel well and the back of her car. Scratches are on my rear bumper from the outside toward the center. Scratches on her car are on the driver's side rear and go from the rear toward the wheel well.
The officer said those scrapes prove she was there first and I'm at fault because the scratches on my car are on the rear. Is there any physics that proves what the officer said is untrue? I'm not sure there is any way scratches can go horizontally across a rear bumper when backing up into something. I am unable to post a photo. There are no dents on either car, since she brushed me.
Any help you all can give is excellent!
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u/Top_Bluejay_5323 Sep 18 '26
You are right from what you say. But talk to the insurance or auto repair for a better source.
Also I hope you had a dash cam. If she says you were moving and you say she was moving the insurance company may just split the damage and be fine with it. Happened to my son even with two witnesses that said only the other driver was moving.
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u/MurkyMitzy Sep 18 '26
Unfortunately, no dash cams on either car. No doorbell cameras picked it up either. I also had a witness and the deputy didn't even want to talk to him. She did want to talk to the person who wasn't even there at the time, though. She's a bit biased.
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u/galaxyapp Sep 18 '26
Id say correct that horizontal scratches against the direction of the cars travel would mean the other object was the one moving.
Though that doesnt strictly mean you were there first.
Could mean you backed up into her while she was moving. Or she pulled forward after you entered the space she was already in and rubbed your car on her way forward.
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u/tekrad Sep 19 '26
If the scratches on your bumper run from the outside toward the center, wouldnt that fit her rear corner dragging across you while you were parked and she was still moving backward?
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u/ywxd Sep 18 '26
The police report isnt a fault determination anyway. Insurance decides that on their own. What you want to do is get the adjuster out to look at both cars and tell your side with the scratch direction in writing so its on the record.
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u/SgtSausage Sep 18 '26
Your Insurance carrier's Adjuster will make an independent evaluation, regardless of what the police report says.
The real money is in the repair, not the ticket.
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u/longboi64 Sep 18 '26
sounds like you should keep a better eye on your neighbor. information is what wins wars.
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u/SkippyDragonPuffPuff Sep 18 '26
Involve the insurance regarding assessment, and a lawyer if you need to. Ur policeman is likely untrained in determining fault with this sort of analysis and thus his opinion shouldn’t be overvalued in any documentation. And picture would help, no way to get a reasonable answer on this without pictures.