Math II Project: Full Stop Ahead
By: Maurissa McNeal
Assume you are traveling on a dry road and have an average reaction time. The formula d = 0.044s2 + 1.1s gives you a safe stopping distance d in feet, where s is your speed in mi/h. Make a table of values for speeds of 10, 20, 30, 40, 50, and 60 mi/h. Then, graph the function.
Here is the table:
Here is the graph of the table:
Suppose a car left a skid mark d feet long. The formulas will estimate the speed s in miles per hour at which the car was traveling when the brakes were applied. Use the formulas to complete the table. Round to the nearest mile per hour.
Here are the formulas:
The estimated speed of the car based on a skid mark with a length of 60ft was about 40MPH on a dry road and about 28MPH on a wet road.
The estimated speed of the car based on a skid mark with a length of 120ft was about 57MPH on a dry road and about 40MPH on a wet road.
Why do you think the estimates of speed do not double when the skid marks double in length? Based on these results, what conclusions can you make about safe distances between cars?
I think the estimates of speed did not double when the skid marks doubled in length because it was two different types of roads.
Suppose you are driving on a dry road with 150 ft (about 10 car lengths) between your car and the car in front of you. Use the formula from Activity 1 to find the maximum speed you should be traveling in order to leave a safe stopping distance.
If I was driving on a dry road with 150 ft in between my car and the car in front of me, the maximum speed that I should be traveling to leave a safe stopping distance is 47MPH.
Work with a group of your classmates to plan a skit that will demonstrate what you have learned about safe distances in driving. Illustrate the relationships among reaction times, road conditions, speeds, and stopping distances. Click on the box below to view the video.