# Homework Help: Why Do We Wear Seat Belts Experiment Help

1. Sep 6, 2008

### BoggyP

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.

2)
http://good-times.webshots.com/photo/2443143040103984762poFErA
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.

Thanks,
BoggyP

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

### mgb_phys

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 ?

3. Sep 6, 2008

### BoggyP

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.

4. Sep 6, 2008

### BoggyP

Last edited by a moderator: May 3, 2017