Thread: Twin headlights
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Old 07-23-2014, 02:00 PM   #57
Sparrowhawk OP
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Joined: Sep 2005
Location: Eastern Washington, USA
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Originally Posted by Sparrowhawk View Post
Here's the puzzle. A person (me) wants to pass a semi and five cars that are going 65 mph in a 70 mph zone. The cars are following each other and the truck about two car lengths apart. I am following the last car about two car lengths back and, because I am such a careful driver, I want to give the truck a full semi length of space before pulling back in. There is an oncoming car about 0.8 miles down the road probably doing 75 mph. As I pass the line of vehicles I will do 90 mph. Is this a safe pass and what will be the distance betweem me and the oncoming car when I pull back into my lane?
No mathematicians in the house it seems. This little bit of elementary algebra (from the Arabic al-jebr, meaning "reunion of broken parts") and arithmetic (from the Greek arithmos, meaning numbers) is just a warm-up to the more important question of "Just how close were those Harley's anyway?" Then we can answer DesertTortoise's question " How long will it take for my passengers to see their life flash before their eyes?"

I have 2 semi lengths, 5 cars, and 6 two-car spaces to pass. I'm going 25 mph faster than the line of vehicles so it takes me about 12 seconds (12 Colorados)to get passed. In that 12 seconds I travel 0.3 miles of the 0.8 mile separation and the oncoming car travels 0.25 miles. If everything works as planned there is a quarter mile between me and the oncoming car when I move back into my lane.

But things do not work out as planned. I saw what I wanted (or expected) to see, not what was actually there. On to part two.
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