11 - Exam 1 Recap _ Freeways

11 - Exam 1 Recap _ Freeways - Exam Recap & HCM –...

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Unformatted text preview: Exam Recap & HCM – Freeways TTE 4004 10/10/11 Exam 1 Recap 2 4 6 8 10 12 14 16 18 20 50 55 60 65 70 75 80 85 90 95 100 105 110 Average = 85 Short Answer Questions Roadway design governed by: Vehicle and human capabilities Role of transportation engineer: Move people and goods safely and efficiently Two opposing forces: Tractive effort and resistance D vs Δ D is for a 100 ft arc of the curve, Δ is central angle of whole curve Aerodynamic resistance: 3 components that across vehicles: Turbulent flow of air around vehicle Friction of air passing over vehicle Air passing through vehicle components What accounts for this? Drag coefficient - C D More Short Answer Crest Curve and 2-lane road Stopping sight distance (object on other side of crest) Passing sight distance Sag vertical curve with bridge Stopping sight distance (headlight sight distance) Underpass sight distance (bridge blocking view) Bridge clearance height ε Gear reduction ratio # of crankshaft revolutions per tire revolution Power for aero resistance ~ speed: v 3 Power for rolling resistance ~ speed: v 2 at beginning, then linear Power for grade resistance ~ speed: linear Problem 1 Does aerodynamic resistance = rolling resistance at any speed between 0 and 60 mph? At what time? R rl = R a Solve for v Use vehicle sheet to find time 2 2 V A C R f D a ρ = W f R rl rl = + = 147 1 01 . V f rl Problem 2 Max acceleration from rest on a downgrade? F = F e or F max What is speed at rest? R a = 0 f rl = 0.01 Downhill Grade resistance is negative F = γ m ma + R a + R rl + R g ( 29 L h L h f l W F rl f max / 1 / μ μ-- = r M F d e e η ε = Problem 3 Distribution of braking forces?...
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This note was uploaded on 12/07/2011 for the course TTE 4004 taught by Professor Staff during the Fall '08 term at University of Florida.

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11 - Exam 1 Recap _ Freeways - Exam Recap & HCM –...

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