Full Stop Ahead Project For Math II
By Jared Duncan and Lee Winstead
Activity One: Stopping Distance
Activity Two: Skid Marks
The following formulas show how to calculate the speed a vehicle was moving by using the length of it's skid marks.
On a dry road: s = √27d
On a wet road: s = √13.5d
Why do you think the estimates of speed do not double when the skid marks double in length?
Because the traction is different in each situation, meaning it takes different amounts of time for the vehicles to come to a full stop.
Based on the results, what conclusions can you make about safe distances between cars?
When driving behind someone while going around 40-50 mph, make sure to keep a safe distance of about 100 feet, so you have time to stop. Keep back even farther if going this speed in wet, frozen, or other traction-lessening conditions.
Activity Three: 150 Foot Stopping Distance
To calculate the speed at which you would need to travel in order to have a stopping distance of 150 feet, you must reverse calculate the formula from activity one. However, I just plugged in a bunch of speeds until I got the right answer, so I don't have any work to show here.
Anyways, to have a stopping distance of 150 feet on a dry road, you would need to be going about 47.21 mph. However, just to be safe, you should go around 45 mph.