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Friday, December 19, 2008

Aggressive Drivers And The Physics Of A Car Crash

In my last article I mentioned that aggressive drivers seem to concentrate on what they feel are unreasonable and unfair traffic laws passed by the state but forget that there are physical laws that come into play when they are driving that they can’t break no matter how hard they try. In this article we are going to take a closer look at those laws and how they come into play in a car crash.

Now this article involves a little math and I flunked high school algebra (twice) so instead of trying to do the math myself, I found a calculator online that I will share with you so you can check the figures yourself.

Let's take the scenario of an aggressive driver driving at 40 mph (in a 30 mph zone) who chooses to run a red light (he will try to say the light was yellow and he didn’t have time to stop). Meanwhile another driver traveling at the posted speed limit enters the intersection on the green light.

Now the first thing we have to consider is how many feet per second the two cars are traveling. The aggressive driver going at 40 mph is covering 58.8 feet per second (fps). The other driver going 30 mph is covering 44 fps. That means that the speed at which they are approaching each other is 70 mph or 102.9 fps.

The average driver’s reaction time is 3/4 of a second. That is how long it takes for them to realize there is a problem ahead. They still have to decide what to do and then act on their decision so, taking the aggressive driver’s lightning fast reactions into account, we will assume that it takes him 1.25 seconds before his foot actually hits the brake. In that time he has traveled 73.5 feet.

Now Newton’s laws of motion come into effect. The first law says that an object in motion tends to remain in motion. Simply put, you can’t stop a 3,000 pound car traveling at 40 mph instantly. It will take about 120 feet before his car can be brought to a complete stop. The other driver is also trying to stop so let’s assume both cars slow by 10 mph to 30 and 20 mph (50 mph closure speed) before the crash.

Using the calculator I found at considering that both cars weigh approximately 3,000 pounds (6,000 pounds combined), the collision force will look like this:

Weight - 6,000 lbs
Speed - 50 mph
Crash Force - 501,779 lbs
Crash Force - 250 tons

Let's take it further and assume that one of the passengers is a girl who weighs 100 pounds. Unfortunately she wasn’t wearing a seat belt. Newton’s laws again come into play and the force of her body hitting the dashboard looks like this:

Weight - 100 lbs
Speed - 30 mph
Crash Force - 3,010 lbs
Crash Force - 1.5 tons

The greater the speed, the less time the driver has to react and the greater the collision forces will be. The aggressive driver’s driving skills and lightning fast reflexes don’t even come into play here. To see the approximate results of this crash click here:

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Be careful out there and drive safe.

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