Calculating the speed of air hitting the bed?

[Specaled]

I'm doing a final physics project for high school involving the speed of which air comes off the top of the truck and hits the truck bed. Is there anyway to calculate that speed? I Drive a 2004 Dodge Dakota 5 speed manual 2wd. The bed is about 80 inches long by 60 Inches wide.

[aerohead]

Originally Posted by Specaled

I'm doing a final physics project for high school involving the speed of which air comes off the top of the truck and hits the truck bed. Is there anyway to calculate that speed? I Drive a 2004 Dodge Dakota 5 speed manual 2wd. The bed is about 80 inches long by 60 Inches wide.

The local airspeed is going to vary depending on where the measurement is taken.
If you wanted to approximate the airspeed at the back edge of the trucks roof,lay out some string from the center of the grill,up over the hood to the cowl,then up the windshield and over the roof the the rear edge.
Now measure that length of string.
Then measure the distance from one of the front edges of either fender,back to the location along the side of the truck even with the end of the roof.Measure that length.
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The distance along the side of the truck will represent your indicated road speed on a calm day with zero wind.
The distance up and over the roof represents the distance covered in the same amount of time.For this air to arrive at the same time as the side flow,but traveling the greater distance, requires a higher average velocity.
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If the 'overhead' string is say 50% longer than the 'straight down the side' string length,then the velocity over the roof,into the bed must also be 50% faster.
So at say 60 mph,on a calm day,the flow over the roof will be 90 mph.This is THE reason for never using a roof rack on a vehicle.