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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


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    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
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