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

Homework Help: Not your average car collision (very real life ) - no values supplied

  1. Aug 17, 2012 #1
    Not your average car collision (very "real life") - no values supplied

    1. The problem statement, all variables and given/known data

    Hi,
    I've been given an assignment on a theoretical car collision. However, it is very "real world" (we are given information regarding the condition of each car before and after [particularly the tyre tread -> coefficient of friction?], and the state of the drivers [reaction time?]).

    Here's the general run down:


    Car B (m = 887kg) skids for 11.38m and comes to a stop in the middle of an intersection.

    Car A (m = 1,495 kg) essentially T-bones Car B. He does slam on his brakes and the skid mark from applying brakes to hitting Car B are 14.5m long.

    The speed limit for the road is 13.88m/s (50kph). Here is where it gets tricky. We are not given any value for velocity. There are witness statements that think this guy has gone faster than the speed limit.


    Car B (assumed no brakes applied) is pushed in a curved line... but I am going to only use the distance between the first point on the curve and the last = 2.935m (so a straight line). As a result of figuring out this straight line it occurs at an angle of 45deg.

    Car A then continues onwards without its brakes applied and comes to rest after a distance of 17.419m.

    2. Relevant equations

    Using http://hyperphysics.phy-astr.gsu.edu/hbase/images/astp3.gif I figured out the stopping distance of the car at any given speed.

    From that I calculated acceleration (will this be constant regardless of speed?)

    From calculating the acceleration (deceleration) I found out how long it took for him to travel the 14.5m, which in turn gave me a value for his velocity upon hitting the car.

    Assuming what I have done is correct, I have no idea how to apply these numbers to the situation DURING and AFTER the collision???

    3. The attempt at a solution

    I just don't know how to tackle this problem. This was assigned while learning our Momentum module.
    So, the end goal is to work out as many mechanical/physical properties of both cars before, during, and after the collision.

    Please note that I am not after an easy answer here. Just some guidance would be really helpful. Especially comment on my derivation of acceleration of his car.




    I can upload the PDF file of the assignment if it makes the picture clearer. The diagram used, however, is not to scale and not a very good representation of the data.




    Thanks for any help (just need a nudge in the right direction :) )


    Karl
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Aug 18, 2012 #2
    Re: Not your average car collision (very "real life") - no values supplied

    Any advice guys?

    I hate to be one of those people that points out the views:comments ratio...buuuut... :P


    Karl
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook