Traffic Question Exploration
Set of focused questions with specific answers 
You are traveling in a 3500 pound Subaru going 65 mph down a straight highway in the winter and the roads are icy. If a stoplight a ways in front of you turns yellow, how long will it take you to stop without skidding?
What is the minimum distance required to stop safely at the light on the icy roads if you are traveling at 70 mph?
How long will it take the car to stop if it skids on wet roads traveling at 55 mph?

Process + Spreadsheet 
Access The Spreadsheet Here
For the focus questions I started with creating a spreadsheet where I could plug in the data and create equations. I got most of my equations from my journal, which was recorded during class. I used these equations to measure the weight in newtons of the car, the force of friction, and the stopping + time of both skidding and normal braking of the car for speeds all the way up to 70mph. The spreadsheet allows me to calculate any friction impacting the car as well as the conditions of the road. For the first question, I first calculated the weight of the car in newtons, using the conversion of 1lb = 4.45n Then I needed to calculate the force of both static and kinetic friction, which is given by multiplying the newton weight by the friction. After finding the force of friction, I needed to find the acceleration of the car, which is pretty simply, it’s just the force of friction divided by the weight of the car in kilograms. force of friction/ (3500* 0.45= kg) After finding the acceleration, I can then calculate braking time, which happens to be the speed divided by the acceleration. To find the speed, I simply convert mph to m/s then divide by the acceleration. For the distance, it’s a little more complicated. Graphing both the speed and time will create a triangle shape, which can help to calculate the distance because if we can find the area of the graph, that is the answer for that speed and time. We can convert this to an equation by using the triangle formula (b*h)/2. Using this we can plug in speed as the base, and time as the height then dividing all of that by 2, giving us the distance needed to stop. 
General Explanation 
By finding the stopping distance of the car on icy roads using the force of friction and acceleration, I can find the minimum time that a light needs to be yellow for the winter. After finding the force of friction for the car and stopping distance, I can change up the weights, frictions, and velocity to account for different conditions. By using a spreadsheet, I can plug in all of the equations that I need and then by changing one to two units I can easily calculate the stopping distance, time, and acceleration.

Some questions to ponder 
Is there a point where it will take longer for the car to stop then the yellow light is on?
Is a 3 second yellow light long enough for a car traveling at 45mph and 100m away to stop? Is there a threshold where the car can’t make the light in time, but also can’t stop before the intersection? 