qz1sol_0132Hf10

# qz1sol_0132Hf10 - v m = at 1 ⇒ t 1 = v m/a = 3.48 s...

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TA: Tomoyuki Nakayama Monday, August 30, 2010 PHY 2048: Physic 1, Discussion Section 0132H Quiz 1 (Homework Set #1) Name: UFID: Formula sheets are not allowed. Calculators are allowed. Do not store equations in your calculator. You need to show all of your work for full credit. ________________________________________________________________________________ A certain elevator cab has a total run of 150 m and a maximum speed of 250 m/min, and it accelerates from rest and then back to rest at 1.20 m/s 2 . a) How far does the cab move while accelerating to full speed from rest? The maximum speed in SI units is v m = 250 m/min × (1 min/60 sec) = 4.17 m/s The time interval for the cab to reach its maximum speed is
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Unformatted text preview: v m = at 1 ⇒ t 1 = v m /a = 3.48 s During this time interval, the cab moves the distance Δ y 1 = (1/2)at 1 2 = 7.27 m b) How long does it take to make the nonstop 150 m run, starting and ending at rest? While the cab is slowing down, it moves the same distance as it does while it is speeding up. Thus the distance the cab travels with its full speed is Δ y 2 = Δ y – 2 Δ y 1 = 135 m, where Δ y = 150 m. The cab travels distance Δ y 2 in the time interval Δ t 2 = Δ y 2 /v m = 32.4 s Since it takes 2 Δ t 1 while the cab is changing its speed, the total time for the whole run is Δ t = 2 Δ t 1 + Δ t 2 = 39.4 s...
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