Dynamics of Algebra 2 Name: ______Date: ______Block: ______Do Now #53

My Cousin Vinny (…and Square Roots)

Vinny Gambini, brilliantly portrayed by , is a Brooklyn attorney who has finally passed the Bar (after repeated failures) and now finds himself defending his nephew and his nephew's friend against charges in . Along with his too beautiful fiancee, played by Academy Award Winner Marissa Tomei, Pesci investigates the southern style of life, as he fathoms southern courtroom procedures in this classic and very funny film that was made in 1992.Notice the heavy accent of the attorney played by Joe Pesci and the southern American accent spoken by the rest of the cast. ______

1) What factors do you think creates tire skid marks on a street?

2) How can tire skid marks be used to determine whether someone committed a crime?

3) Solve for x using Pythagorean Theorem:

x 6

8 MATH FIGHTS CRIME

Fighting crime — perhaps not the first thing that springs to mind when you think of maths. Ask someone on the street what they think about maths and unfortunately their answer may well be:"Maths is boring", "Maths is exact", "Maths is irrelevant", or even "Maths is scary"

Maths may seem very different from the confused, unpredictable and highly relevant business of fighting crime. But in fact maths is very relevant. It is integral to many of the methods police use to solve crime, including dealing with fingerprints, accident and number-plate reconstruction and tracking down poison.

Math fights crime

Let's step into an ordinary day in the life of a police unit and see how mathematics can help fight crime. First up, we are investigating a car accident and need to answer the question: was the car speeding?

The evidence available is the collision damage on the vehicles involved, witness reports, and tire skid marks. Just like on television, examining the skid marks can help reconstruct the accident. The marks are caused by the speed of the car as well as other factors such as braking force, friction with the road and impacts with other vehicles.

Mathematically we can use mechanics to model this event in terms of , the length of the skid, , the speed of the vehicle, , the acceleration due to gravity and , the coefficient of friction times braking efficiency. The model links the cause (the speed of the car) to the effect (the distance of the skid): This can be rearranged so that given the skid distance we can mathematically determine the speed of the car, usually giving a lower bound:

But for this to work, we need to have an accurate estimate of , the value describing friction and braking efficiency

Let’s Investigate 2 The formula 0.83v = s is used to approximate the velocity v in miles per hour of a car based on length of its skid marks s (in feet) on wet pavement.

1. If the tire skid marks are 53.12 feet long, how would you find the velocity of the car?

2. The tire skid marks of car A is 40.67 feet, while car B is 29.88 feet long. Which car has a greater velocity? Why?

3. Police Officer Charlie says that if the tire skid mark’s length (s) is given, there are two possible values of the velocity v. One value of v is positive and the other is negative. Do you agree with Charlie? Explain why or why not?

My Cousin Vinny

Intro to the Crime (3:45-5:45): http://www.youtube.com/watch?v=pFOnB9ODRkA&feature=email

Use of skid marks (whole clip) http://www.youtube.com/watch?v=nwEAR2BmD1E&feature=email