PostedMidQ2

# PostedMidQ2 - 1 On HW5 designers now change the length of...

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1. On HW5, designers now change the length of spiral Ls to 600 ft, while setting the radii Rc for Curve 1 and 2 to 1200 ft. The design velocity Vdes that will give a "jerk" of 2.0 ft/sec^3 is most nearly: @ Vd = (Rc*Ls*C)^1/3 = 76.993 mph a. 72 mph *b. 77 c. 82 d. 87 2. For the design values above in #1, the rectangular spiral component Xs is most nearly: @ must be slightly less than 600, DELTAs=Ls/(2*Rc) radians, and by the infinite series: Xs = Ls*(1 – DELTAs^2/ (5*2!) + DELTAs^4/(9*4!)-+...) = 596.26 *a. 596 b. 598 c. 600 d. 602 3. On our HW5, which will compute the correct value of station for the T.S. for the second curve (Sta TS2)? @ Sta TS2 = Sta ST1 + (TTL2-Ts1-Ts2), must compute the straight line distance on TTL2. a. Sta PI1 + Ts1 + Ts2 b. Sta PI2 – Ts1 c. Sta 40+00 – TTL2 + Ts1 + Ts2 *d. Sta ST1 + (TTL2-Ts1-Ts2)

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4. On railroads and other fixed guideway route systems, spirals are absolutely needed because of: @ the "infinite jerk" force build up at the PC without spirals. a. national design standards *b. rapid lateral force build-up c. a natural spiral in the tracks d. rail spacing and geometry 5. If the spiral design values of problem #1 were used to insert spirals into Curve 2 of SR25, the length of the remaining circular curve is most nearly: @ DELTAc=DELTA(32 deg) – 2*DELTAs = 0.058. Lc=Rc*DELTAc = 70.2 feet *a. 70 ft b. 100 ft c. 130 ft d. 160 ft
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