272_Dynamics 11ed Manual

272_Dynamics 11ed Manual - Engineering Mechanics - Dynamics...

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Unformatted text preview: Engineering Mechanics - Dynamics Chapter 14 Solution: h⎞ θ = atan ⎛ ⎟ ⎜ P = F v sin ( θ ) ⎝l⎠ v= P M g sin ( θ ) v = 0.285 m s *Problem 14-48 An electric streetcar has a weight W and accelerates along a horizontal straight road from rest such that the power is always P . Determine how far it must travel to reach a speed of v. Given: W = 15000 lbf v = 40 ft s P = 100 hp Solution: P = Fv = ⎛ W ⎞a v = ⎜⎟ ⎝g⎠ Guess d = 1 ft Given d ⌠ ⌠ ⎮ P dsc = ⎮ ⎮ ⌡0 ⌡ ⎛ W ⎞ v2⎛ d v⎞ ⎜⎟⎜ ⎟ ⎝ g ⎠ ⎝dsc ⎠ v ⎛ W ⎞ v2 dv ⎜⎟ ⎝g⎠ d = Find ( d) 0 Problem 14-49 The crate of weight W is given speed v in time t1 starting from rest. If the acceleration is constant, determine the power that must be supplied to the motor when t = t2. The motor has an efficiency ε. Neglect the mass of the pulley and cable. Given: W = 50 lbf v = 10 ft s t1 = 4 s t2 = 2 s ε = 0.76 g = 32.2 ft 2 s Solution: a= v t1 v2 = a t2 a = 2.5 ft 2 s ft v2 = 5 s 270 d = 180.8 ft ...
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This note was uploaded on 08/16/2011 for the course EGN 3321 taught by Professor Christianfeldt during the Spring '08 term at University of Central Florida.

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