1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Mysterious car accident

  1. May 29, 2009 #1
    I was in a car accident involving an eighteen-wheel truck. The driver thinks the truck hit the car. I was in the passenger seat and I think the car hit the truck. Can someone give their opinion given the details:

    The car was traveling in the left lane at about 70 miles on the highway. The truck was next to the car in the right lane. Suddenly, the car started veering slightly out of its lane to the left. I was very suprised and looked over at the driver to ask what was happening. There was no sound or push or vibration at all. Then the car swung to the right perpendicular to the truck's middle part. The truck was directly in front of us and I think part of the car's hood went under the truck. At this point, the car began spinning and flipped about three times before landing in the median facing the opposite direction. Miraclously, there were no major injuries but the car was totalled.

    The reason I believe the truck did not hit us is because there was no sound or vibration at all before the car swung to the left. It was a huge truck and I've been rear-ended, so I know if you get hit, you will hear the noise and you will feel the impact when you are hit even by a small car at a low speed. The police report states that the car veered out of the lane and overcorrected itself, but the driver insists the truck hit us. Can anyone offer their opinion by applying some physics knowledge? Thanks.
  2. jcsd
  3. May 30, 2009 #2


    User Avatar
    Science Advisor

    You could see whether or not there are any paint chips (in an appropriately sized dent) from the car you were in on the truck. There would also be transferrance from the truck on your car (in another dent). You could've been caught in the truck's wake, but I have a hard time believing that'd be enough to knock you out of your lane (unless you were in a really, really light car).

    Most likely, your driver friend got caught slightly unawares (drowsy, sun in eye, whatever) saw the truck at very close range, and then panicked / jerked and overcorrected, as the police report suggests.
  4. May 30, 2009 #3

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2017 Award

    There are professional accident reconstructors. You might want to consider hiring one.
  5. May 30, 2009 #4
    Cars are heavy in front so an overcorrection which caused a skid will tend to continue momentum through the axis of the skid perpendicular to the front line of the car over the wheels. The back wheels do not support as much weight and when friction overcomes momentum the car will tip. This is especially true if any part of the back end came off the finished road onto any warning strips. The friction caused both the roll and yaw of the car around to 180 degrees from facing the truck as the lighter rear end of the car overcame the momentum of the front end. Say a prayer, you're a lucky person.
  6. May 30, 2009 #5
    Several times on the highway my car has been pulled towards another lane quite sharply in the wake of a passing truck, and it is only due to heavy over-correction that I prevented that. Given those experiences I would not at all be surprised if a truck turned sideways could create an even bigger wake
  7. May 30, 2009 #6
    I've noticed that driving next to a truck in windy conditions, especially gusty winds, can be touchy. What where the weather conditions?

    The VW bug was one of the worst with the engine in the rear, for suprise lane changes while entering and exiting underpasses--and driving next to trucks. What model car were you in?
  8. May 31, 2009 #7

    Ranger Mike

    User Avatar
    Science Advisor
    Gold Member

    IMO, something may have broke on the steering. How many miles did the car have on the odometer? A worn out tie rod can break on you and this would have caused the right side pull. Thing two- the truck has one heck of a lot of mass. If it was traveling at 55 MPH and there were not skid marks from its tires, the driver probably was maintaining the speed. If the nose of your car was under his trailer rails, I would say you prob hit him. Things happen real quick at 70 MPH..u are pretty luck..I roled severla cars in my youth..was fun but mucho $$$
    good luck
  9. May 31, 2009 #8


    User Avatar
    Homework Helper

    The side winds from a truck aren't normally strong enough to cause this problem, at least not with most cars. I drive a motorcycle and have experiemented by positioning the bike in various parts of the wind flow off a truck, and never experienced loss of control, but could feel the wind. Then again, modern motorcyles are designed for high speeds (186 mph, speed limiter in the case of the fastest bikes), and are very stable. An old VW van would be a problem in any wind.

    If there was real side wind blowing from the right to left at the proper angle, there is a small chance that the side wind and truck movement combined to generate a vortex, a spinning wind that could cause a small car to yaw to the left in addition to the side wind also creating a linear force to the left. I've never experienced this, but I guess it could happen with strong gust of side wind.

    Depending on the car and suspension, if the suspension had too much play, either the side wind and/or yaw could have loaded up the suspension so that even a minor correction caused the car to spin to the right.

    But that would mean that Nascar doesn't have real race cars, oh wait, never mind.
  10. May 31, 2009 #9
    It was a Toyota Corolla year 2000. There was a passenger in the back as well and the trunk and back seat were filled with things as we were moving. Someone did mention that maybe it lost balance because the car is light. However, if the truck had hit us, wouldn't there be a large noise and vibration from such a huge mass at a high speed, and I'm guessing the car would have travelled to the left since the truck was on the right. It doesn't make sense since we originally swerved left, then to the right, into the truck.
  11. Jun 1, 2009 #10


    User Avatar
    Science Advisor

    I don't think this would help, since it is already known that the car did hit the truck with the car facing right (relative to the roadway) and the truck moving forward along the roadway. This means there will be dents, with paint chips in them, on the right side of the car. But you mention that the car came in from the side and hit the truck near the middle. If you find dents or scrapings on the truck forward of that location, this could be a good indicator.

    The fact that you did not hear or feel the impact is not a reliable test. However, you say that you looked over at the driver when the car swerved left; where were you looking and what were you thinking about just before that (if you can remember)?
  12. Jun 1, 2009 #11
    Just before we swerved to the left, we were being tailed by another car and we wanted to pass the truck and get in front of it so the car behind us could pass. I was watching the truck and the car behind us when I noticed us swerving left, and my immediate thought was something was wrong with the tires.
  13. Jun 1, 2009 #12
    and the weather conditions seemed pretty normal, no strong winds. I think getitright's explanation makes a lot of sense.
  14. Jun 2, 2009 #13
    From the information you supplied my best analysis is that the car you were in was behind a truck and wanted to pass. In doing so during the acceleration you pulled in front of another vehicle who's driver had made that same decision a second earlier. Perhaps only the slightest bump caused the drift to the left. Then your course took you on what I can only describe as a parabolic course of the front wheels during the parabola included a very good look at the structure of the truck. Can't add anything more without more information. Best of luck.God bless.
  15. Jun 3, 2009 #14


    User Avatar
    Science Advisor

    That might be a good place to start; what part of the truck were you looking at? I mean, how far up the length of the truck had you gotten before the swerve left? And where did your front end hit the truck when you swerved back to the right? If there is paint from your car forward of that spot, then the truck definitely hit you.

    However, it seems like if you were looking at the truck when the leftward motion began, you'd have been aware if it hit you.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook