1D3

= Evidence =

GROUP CONTRACT:
Signatures: Emeline Liu 01 Matt Margolis 02 Brian O'Flaherty 03 Chrissy Taylor 04

GROUP LOG:

 * __Tuesday, April 20, 2010__:** Discussed and created group contract and rules. We each were assigned individual roles. Emeline is the attorney, Matt is the police officer, Brian is the expert witness, and Chrissy is the Assistant Attorney. Emeline was elected as the group leader, also.


 * __Thursday, April 22, 2010__: Read and discussed ELVA book.

**__**Friday, April 23, 2010**__**:**** Went the crash scenario in greater detail. **

__**Monday, April 26, 2010**__**:**** Complete PRT lab at home. **

__**Wednesday, April 28, 2010**__**:** ** Discussed results and findings PRT. Began crush lab and force of friction lab. **

__**Thursday, April 29, 2010**__**:**** Created evidence page and filled in the given information from the scenario. Crush lab is almost finished, and Brian will complete it at home. Force of friction lab is finished and posted; we found the value of Mu. Skid marks were measured, scaled, and added to the evidence page. **

__**Friday, April 30, 2010**__**:** ** Crus h lab was completed and discussed. We came to an understanding about which skidmark should be measured and considered in our calculations. Also, we started the calculations to find the initial velocities of the cars, which Emeline then finished during lunch. Our calculations so far are very interesting. Although we did achieve a lot, plans were made to meet over the weekend to write and polish our arguments. We also have to organize and post our calculations to our evidence page.

**__**Sunday, May 2, 2010**__**:** We are all together at Chrissy's house. We are reviewing the calculations for the speed of both cars, making a powerpoint, and taking pictures at the scene.

FRICTION LAB:
Exhibit A Exhibit J
 * [[image:oh_yaaa.png]]

Asphalt Mass of wood with tire=.997 Kg Mass of 10 lb weight=4.436 Kg Combined Mass=5.533 Kg Acceleration due to gravity= 9.8 m/s^2 Force of Friction=39.1 N Exhibit I

****Wet Grass**** Mass of wood with tire=.997 Kg Mass of 10 lb weight=4.436 Kg Combined Mass=5.533 Kg Acceleration due to gravity= 9.8 m/s^2 Force of Friction=37.3 N **

REACTION TIME LABS:
Sf = (1/2)at^2 Sf = distance that ruler falls a = acceleration (due to gravity) t = time ruler takes to fall in seconds (reaction time)
 * Reaction Time Lab- Chrissy Taylor**
 * = Trial ||= Distance Fallen (m) ||=  ||= Time (s) ||= PRT ||
 * = 1 ||= 0.15 ||=  ||= 0.1745 ||= 1.745 ||
 * = 2 ||= 0.18 ||=  ||= 0.1917 ||= 1.917 ||
 * = 3 ||= 0.16 ||=  ||= 0.1807 ||= 1.807 ||
 * = 4 ||= 0.19 ||=  ||= 0.1969 ||= 1.969 ||
 * = 5 ||= 0.20 ||=  ||= 0.2020 ||= 2.020 ||

Vo = Initial velocity (0) So = Initial distance (0) [Cancel out from the equation because it falls from rest at no distance]

From this experiment, I determined that my average PRT was 1.892. Whilst conducting this experiment, I realized that the longer I anticipated the dropping of the ruler, the longer it took for me to react. My PRT would be higher, since I was less alert. When the ruler was dropped quicker, my reaction time was quicker

Equation Used to Determine Reaction Time: Sf = (1/2)at^2 + Vot + So Sf = Distance that ruler falls in meters a = acceleration (due to gravity) t = time taken for ruler to fall in seconds (reaction time) Vo = Initial velocity (0) So = Initial distance (0)
 * Reaction Time Lab- Matt Margolis**
 * Trial || Distance Ruler Falls (m) || Reaction Time (s) || PRT ||
 * 1 || .15 || .1750 || 1.750 ||
 * 2 || .20 || .2020 || 2.020 ||
 * 3 || .18 || .1917 || 1.917 ||
 * 4 || .20 || .2020 || 2.020 ||
 * 5 || .29 || .2433 || 2.433 ||
 * 6 || .30 || .2474 || 2.474 ||
 * 7 || .28 || .2390 || 2.390 ||
 * 8 || .20 || .2020 || 2.020 ||
 * 9 || .25 || .2259 || 2.259 ||
 * 10 || .21 || .2070 || 2.070 ||

I tried to do this activity using a ruler and keeping my fingers at the 6 inch mark, but every time it proved to be unsuccessful as I wasn't able to catch the ruler in time. So I then put my fingers at the very bottom of the ruler and when my Dad dropped it I caught it every time. The distances varied depending on how concentrated I was. From this activity I can conclude that depending on the state of mind the driver is in and how concentrated he/she is will have a significant impact on the reaction time. Also, if you see a car stopping you aren't going to instantly slam on your breaks and prevent an accident, it takes time to process events that you can't predict.

This experiment showed that reaction time depends on so many variables - level of concentration, how tired a person is, level of noise. I did the lab while tired, which explains why my reaction time is higher than the average of 1.5 for most people. Also, during the experiment, the only thing I had to concentrate on was catching the ruler - when driving, a person has many more things to keep track of, which may change the real-time reaction time. While the lab helped convey a basic understanding of reaction time, the real reflexes of a person in an car may be different.
 * Reaction Time Lab - Emeline Liu**
 * Trial || Distance fallen || Reaction time (s) || PRT ||
 * 1 || 0.2 || 0.20 || 2.02 ||
 * 2 || 0.21 || 0.21 || 2.07 ||
 * 3 || 0.19 || 0.20 || 1.97 ||
 * 4 || 0.16 || 0.18 || 1.81 ||
 * 5 || 0.18 || 0.19 || 1.92 ||
 * ||  || Avg PRT || 1.96 ||
 * ||  || Avg PRT || 1.96 ||


 * Brian O'Flaherty's Reaction Time Lab**


 * Trial || Falling Distance (m) || Reaction Time (s) || PRT ||
 * 1 || .18 || .192 || 1.92 ||
 * 2 || .16 || .1807 || 1.807 ||
 * 3 || .15 || .175 || 1.75 ||
 * 4 || .15 || .175 || 1.75 ||
 * 5 || .18 || .1917 || 1.917 ||
 * AVG || .164 || .18288 || 1.8288 ||

I redid the Reaction Time Lab to fit the formula S = 1/2gt^2. In meters, my distances ranged from .15 cm to .18 cm and my reaction time ranged from .175 seconds to .192 seconds. What does this mean in terms of an accident? A car traveling at 60 mph would travel an extra 5 or 6 meters before stopping due to reaction time, and this distance could be life or death.

MEASURING CRUSH ENERGY LAB:


= ACCIDENT SCENE: = Exhibit C Exhibit D Exhibit E

Exhibit F

Exhibit G