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!

Homework Help: Why Do We Wear Seat Belts Experiment Help

  1. Sep 6, 2008 #1
    1. The problem statement, all variables and given/known data
    Ok so we did an experiment in class.
    We took a wooden board, and put it on an incline. We put a car on top of the board with a man made of play-doh. We put a barrier on the board so that the car would crash and the man would fall off. This has to do with the topic "why do we wear seat belts?" I did the experiment and most of the write up but I'm not sure about a few small things.
    1) Free body diagrams on the passenger before & during the collision.
    2) Makes curve of best fit on our graphs.

    2. The attempt at a solution

    1) For before the collision I know the gravity and normal force were i believe equal, since he was sitting on the car. I think that's all but not sure.
    For during the collision the apparent force > friction force? and gravity > normal? I think it's true because gravity pulls you back down and the friction you get when flying though air is very small.

    http://thumb2.webshots.net/t/50/750/6/5/40/2220605400103984762TULVjX_th.jpg [Broken]
    Well I have to plot distance down the ramp vs. distance the man went before he stopped & Distance vs. Speed of the car (based on ticker taping).

    3. Important Facts

    The car was like a brick with wheels a man made of play-doh sat on the top near the front.

    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Sep 6, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    The force diagram is a bit tricky.
    Without a seatbelt there is no force acting on the driver, he/she continues in a state of uniform motion until his/her head hits the windscreen!

    What are you plotting to fit a straight line to ?
  4. Sep 6, 2008 #3
    The car we used was flat so during the crash in the air, there are no forces? What about when he hits the ground & roles (since he isn't human). I think he means in the air, but I already sent my teacher an email asking which, i'm waiting for him to get back to me.

    I uploaded the graphs which should help and I made lines on the computer of an estimate but not sure.
    also correction *curve* of best fit.
  5. Sep 6, 2008 #4
    Last edited by a moderator: May 3, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook