Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I need some help from smarter people than I

  1. Nov 18, 2008 #1
    Heres my problem. I don't like lawyers, but I know they have their place in this world. I just don't believe that they should be paid 33 1/3 % ( plus expenses totaling 50%) for any awards by the courts for an injury claim, when the poor person is the one suffering.

    I was rear ended while stopped at a stop light by a male driving a 1991 Toyota Chorolla approx gross vehicle wieght 2400 lbs. I was fully stopped with my foot on the brakes in a 1990 Jeep Cherokee Lararo that is raised 2 inches and with a GVW of approx 3800 lbs.

    I am trying to determine how fast he would have been travelling at time of impact to move me about 3 1/2 feet?

    Does anyone know the formula or the answer to this?

    You see I know the formula if there is skid marks, but he wasn't going that fast and didn't even try to stop, so there were no skid marks.

    I now have three bulging discs in my lower back and the Doctors say it may or may not be caused by the accident, because I'm 48 years old and this can happen with age .

    Please help!!
  2. jcsd
  3. Nov 18, 2008 #2
    This is what we in the physics community call a... collision

    There are a few things we need to know, including
    Was the ground level?
    Did his car stick to yours on impact?
    What were the road conditions? (anything affecting slipperyness, including leaves)

    Pictures would be helpful.
  4. Nov 18, 2008 #3
    The road was dry, on pavement and at a level controlled intersection. His car did not stick to mine. He just hit and I was moved 3 1/2 feet from what to officer told me when I was in the hospital I was taken away to hospital before I could get any pictures.
  5. Nov 19, 2008 #4
    m is your car's mass. M is his car's mass. g is the acceleration due to gravity. u is the coefficient of kinetic friction. v is the velocity of his car at the time of impact. x is the distance your car went

    I will be using u values of .6 and .8 because friction can be touchy. It should be somewhere around .7 for normal car tires on a dry road. All equation assume he was coasting when he hit you and rely on the accuracy of your statements regarding car mass and the distance your car was pushed.

    First, I'll calculate the maximum speed he could have been traveling, using an ideal elastic collision and a u value of .6 (he was definitely going faster than this)

    v=sqrt(2mgux/M)=10 mi/h

    Next, I'll calculate the minimum speed he could have been travelling, using an inelastic collision and a u value of .8 (he was definitely going slower than this)

    v=(M+m)sqrt(2gux)/m=13 mi/h

    These two numbers are much closer to each other than I was expecting, but the physics doesn't lie. It looks like he was trying to stop. Could he have had antilock breaks? They reduce skidding.

    Also, I would recommend getting a lawyer. No matter how correct your equations are, if you aren't trained in physics, the jury isnt going to buy it.
  6. Nov 19, 2008 #5
    Tkanks Savant. thats a great help.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: I need some help from smarter people than I
  1. I need some help (Replies: 1)