1. Not finding help here? Sign up for a free 30min 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!

Head-on-collision badly needs help understanding

  1. Sep 23, 2009 #1
    1. The problem statement, all variables and given/known data
    An SUV is travelling north-east bound slightly downhill with a speed of 30kph around a blind curve then a sedan travelling south-west encroached an oncoming traffic with a speed of 80-90kph. There is a head-on collision and the point of rest of both vehicles is in south-west lane / just on the shoulder of the sedan lane where they are parallel to each other. There were no skid marks.

    How did both cars manage to rest at the south-west lane?


    2. Relevant equations
    P = m x v = mv


    3. The attempt at a solution

    I'm not a physicist and I'm trying to help my friend who had an accident.

    Base on my research and my attempt grasp on physics an inelastic head-on-collision happened upon the principal impact. Both cars has an equal momentum upon the collision however because it's downhill and considering the mass of the SUV, the SUV pushed the sedandownwards. The sedan made a clockwise rotation before both vehicles reach the point of rest.
     
    Last edited: Sep 23, 2009
  2. jcsd
  3. Sep 23, 2009 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi anaisnin! Welcome to PF! :smile:

    I'm sorry, but without skid marks on the road, there's almost nothing you can do to work out what happened.

    (why do you want to know anyway … surely if one vehicle was on the wrong side of the road on a blind curve, as you say, then that vehicle was at fault?)

    Are you sure they had an equal momentum? That would make the SUV about 3 times as heavy as the sedan. And how do you know the speeds?

    And you haven't said which way the road curved, nor whether this is driving on the right (as in USA) or on the left (as in UK).
     
  4. Sep 24, 2009 #3
    Re: Welcome to PF!

    hi tiny tim! thank you for the quick reply!

    I'm sorry, but without skid marks on the road, there's almost nothing you can do to work out what happened.
    ive read an article that the possibility of not having skid marks is that a car quickly encroach the oncoming traffic so there's no way for both vehicles to avoid each other.


    (why do you want to know anyway … surely if one vehicle was on the wrong side of the road on a blind curve, as you say, then that vehicle was at fault?)

    my friend was driving the SUV and he was on the lane of the blind curve. however he knows the area too well that's why he slowed down around the curve. the accident happened around past midnight and the area was poorly lit however he saw reflectorized warning already. in his story it happened so fast that he didn't step on the brake, thus the absence of skid mark.

    my friend is in an on-going trial now. since i live in a country with corruption that is rampant, one can easily pay the police investigator to be biased on the report. so on the report my friend was the one who encroached the other lane. however, the police here are not really trained well as compared to other countries -- he took the pictures of the vehicles via cellphone. he didn't even take the pictures of the debris, nor draw the scaled sketch of the accident. and worse we don't even have accident reconstructionists here.

    he asked me to help me do research to prove his innocence.


    Are you sure they had an equal momentum? That would make the SUV about 3 times as heavy as the sedan. And how do you know the speeds?
    In my assumption both vehicles have equal momentum despite the mass of the sedan because the sedan was running too fast.

    could it be the driver of the sedan was countering the centrifugal force? after the impact the wheels of the SUV was 30degrees right while the sedan was in 40degrees left.

    my friend took a video of cars at the accident area in broad daylight. almost most of the cars on the south-west lane/ sedan lane encroach the oncoming traffic.

    now my question is how did both vehicles reach the other side of the road and parallel to each other? i don't know other methods in physics that would determine as such. what could be the other probabilities? if i post an illustration would it be better understanding it?


    And you haven't said which way the road curved, nor whether this is driving on the right (as in USA) or on the left (as in UK).

    this is on the right (as in USA).


    thank you again tiny-tim. i hope others would shed light to this.
     
    Last edited: Sep 24, 2009
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook