Question 321799: If a car is going 30 mph, how long does it take for a car going 50 mph to pass it?
fcrater@gmail.com Found 2 solutions by Alan3354, solver91311:Answer by Alan3354(69443) (Show Source):
You can put this solution on YOUR website! If a car is going 30 mph, how long does it take for a car going 50 mph to pass it?
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Define "pass it"
Depends. Let's say that you define the length of time it takes to pass as the elapsed time from when the front bumper of fast car is even with the rear bumper of slow car until rear bumper of fast car is even with front bumper of slow car.
Now all you need to know is the length of the two cars. Very roughly speaking, passenger cars have lengths that vary from about 13.5 feet for subcompacts to 17.25 feet for full-sized luxury cars.
Let represent the sum of the lengths of the two cars. From the data above this ranges from about 27 feet to 34.5 feet.
The difference in speeds is 20 miles per hour, so the question becomes how long does it take an object moving 20 miles per hour to traverse distances in the range of 27 feet to 34.5 feet?
where is in feet, and is in feet per second.
20 mph is 29 1/3 feet per second. So, depending on the lengths of the two cars involved:
So, if you are running down the road and somebody comes up behind you fast, if from the time their front is even with your rear to the time their rear is even with your front, it takes about one second (the time it takes to say "one-one thousand") then they are going about 20 miles per hour faster than you are. It doesn't matter what speed you are traveling either. If you are going 25 and they pass you in one second, then they are going 45. If you are going 75, then they would have to be going 95.
