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Unformatted text preview: − = − − = The rear of the platoon is moving forward with a speed of 2.5 mph with respect to the roadway. (b) As the front of the platoon is moving forward with a speed of 12 mph, therefore, the length of the platoon is growing at a rate of (12  2.5) = 9.5 mph. Time to travel 2 miles for the truck is hr 6 1 12 2 = , so the length of platoon when the truck turns off is 58 . 1 5 . 9 6 1 ≈ × miles (c) After the truck turns off, the front of the platoon moves with a speed of mph 6 100 50 200 , 1 500 , 1 2 3 2 3 − = − − = − − = k k q q U front The rear of the platoon moves downstream at 2.5 mph and the front of the platoon moves upstream to the rear at 6.0 mph. So time to dissipate the 1.58 miles platoon is 1.58/(2.5+6.0) ≈ 0.186 hr ≈ 11.2 min....
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 Spring '09
 Lee

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