# Physical effects of car collisions on metals

1. May 22, 2013

### Terryski

Trying to understand what happens upon impact to the metal of a car that is stopped (Vehicle 1)when another car's driver's side rear (Vehicle 2) impacts the stationary car . Vehicle 2 is a heavier, larger car and is moving in reverse at approximately 10-15 MPH. The impact site on Vehicle 1 is just in front of the passenger side wheel well. There is a small dent and a large scrape on Vehicle 1. Vehicle 2 sustains minor damage, mostly scrapes. From a physics perspective, it it possible for vehicle 2 to ride up slightly on the front fender of vehicle 1 at the time of collision? Trying to explain why when the vehicles are separate, the impact and scrapes on vehicle 1 are approximately 2 -3 inches higher than those on vehicle 2. Any explanation?

Last edited: May 22, 2013
2. May 22, 2013

### Staff: Mentor

Let me guess, you got in an accident, and are trying to prove it was the other driver's fault...

3. May 22, 2013

### Terryski

Actually he admitted fault but he claimed he hit my daughter directly in the rear of the car. Car wasn't even facing that way. His paint is on the right front fender where he hit her. But, insurance company says the dent and scrapes on our car are higher than where the damage is on his. This actually may become an insurance fraud claim as the ins co had their repair shop write up an estimate for damages that don't exist. If I am summoned to go to court, I need to be able to accurately describe how the slight difference in height could have occurred. Can anyone assist?

4. May 22, 2013

### physwizard

Okay first you need to draw a diagram and explain exactly how things happened. Second, you need to check both cars to see what could have made those scratches in the first place. Any protrusions on either car which could have caused the scratches? Third, I hope you didn't make the scratches yourself just to claim insurance.

5. May 22, 2013

### Terryski

I've worked in insurance myself for 29 years and I AM the one reporting it as insurance fraud. WE ARE NOT MAKING ANY MARKS ON OUR CAR! The man and his body shop are perpetrating insurance fraud by claiming damage where there isn't any!!! We took pictures to show where the damage actually occurred and I have been asked to provide a reasonable explanation. I have filed an accident report with our state as well as notified our State Attorney General's office. I am looking for assistance, not accusations and having majored in science, I felt a person well versed in Physics may be able to help. We have diagrams but I cannot afford to hire an accident reconstructionist at \$3000 or more!

Last edited: May 22, 2013
6. May 22, 2013

### QuantumPion

Do you have photographs of both vehicles at the time of the collision?

7. May 22, 2013

### 256bits

Well you don't make much sense. You say Vehicle 2 is travelling in reverse, and then ask if vehicle 1 can ride up the front fender of vehicle 2, which would make the contact on 2 higher than 1. At a speed of 10 to 15 mph there should be more noticible damage than a small dent and a few scraps, unless you are referring to a grazing type of collision.

For diference in height, perhaps the road surface was uneven where the collision occured, such as a depression or raised bump.

8. May 22, 2013

### Terryski

Sorry, had to correct typo. Wrote initial post as I got off the phone from filing some papers for the claim. Trying to determine if the marks on vehicle 1 could have been higher than scrapes on vehicle 2 (the one travelling in reverse). It appears to have been a grazing type of collision, except for the initial point of impact on vehicle 1. Someone had suggested a model using an inclined plane as vehicle 1 which would show how the larger vehicle could have initially risen then fallen, thus causing the dent, then scrapes. I will go to the scene and check the surface of the parking lot. Thank you.

9. May 23, 2013

### physwizard

The exact shape of the scrapes (whether they are straight or go up and down or are curved, the angle which they make with the horizontal, etc.) could tell you a lot about how the collision took place. (Provided it did happen and you are not making it up.) Also check for any protrusions or sharp edges on either vehicle which could have made those scratches.

10. May 23, 2013

### xxChrisxx

Do nothing, say nothing. Try to give an technical explanation and you'll get butchered because you obviously aren't an expert at this and neither are we.

The thing is you cannot accurately describe anything as to how this occurred. Asking a bunch of people on the internet to give possible explanations is only likely to land you in the....

Stick to describing what you know, not what you think.

Also don't their insurance talk to your insurance? Who actually do have experts on hand.

11. May 23, 2013

### BobG

I would expect the scrapes on vehicle 2 to be higher than the dent on vehicle 1. If he saw the vehicle behind him at the last instance and suddenly put on the brakes, his rear end would dip.

Or, if vehicle 1 was stationary at the time of impact because he instinctively put on his brakes when he realized he was about to be rammed, then his front end would dip at least a little. His statement wouldn't be technically inaccurate, even if not as complete a description as, "I quickly pulled behind the rear moving car and stopped right behind him where he'd be sure to hit me!"

As to a speed of 10-15 mph causing more damage than actually occurred, you should consider how bad people are at estimating speed. Does a speedometer even register a speed when you're moving in reverse? And if it does and the driver of vehicle 2 knows precisely how fast he was travelling in reverse, is that a pretty good indication of why he didn't see the car behind him? I would tend to interpret the speed as meaning he was going slow - i.e. backing up at a speed you'd expect him to back up at.

Backing up while looking forward isn't as unthinkable as it sounds - especially for elderly drivers that have a hard time twisting around to see behind them. I imagine many good drivers have no idea whether their speedometer works when they're backing up, but that's based on the assumption that I'm a good driver. :tongue2: