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PHYS 125 Winter 2008 Exam 1 01/31/2008 - 2 - Form #1 1. As a NASA intern, you are part of a design team developing a new liquid fuel rocket engine. The design engineers have determined that the fuel pumps can deliver fuel and oxidizer (all of which will be expelled out the engine nozzle as the engine operates) at a combined total rate of 100 kg/s. There are four possible fuel/oxidizer combinations which produce different final exit speeds v from the nozzle: Combination I: v = 50 m/s Combination II: v = 75 m/s Combination III: v = 100 m/s Combination IV: v = 125 m/s If the engine must produce a minimum thrust of 10,000 N, the fuel/oxidizer combinations that will meet this specification are: A) **III and IV B) None of the fuel/oxidizer combinations will produce the required minimum thrust. C) I and IV D) All of the fuel/oxidizer combinations will produce the required minimum thrust. E) II and III 10,000 N = (100 kg/s) 100 m/s exhaust Thrust min min Solution 1: III and IV will both produce sufficient thrust. See the notes from Lecture # 5. p m Fv v v tt Δ Δ == = ΔΔ G G fi Solution 2: Displacement Does depend on the See notes from Lecture # 2. rrr ≡Δ ≡ − ⇒ G GG not distance traveled between P and Q. 2. A particle follows a curved path between P and Q as shown below. The displacement of the particle does not depend on A) the direction of Q from P.
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