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Unformatted text preview: alexander (jra2623) oldhomework 23 Turner (92510) 1 This printout should have 13 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points A uniform bar of length L and weight W is attached to a wall with a hinge that exerts a horizontal force H x and a vertical force H y on the bar. The bar is held by a cord that makes a 90 angle with respect to bar and angle with respect to wall. L W What is the magnitude of the horizontal force H x on the pivot? 1. H x = 1 2 W cos 2 2. H x = 1 2 W sin 2 3. H x = 1 2 W sin 4. H x = 1 2 W tan 5. H x = 1 2 W cos 6. H x = 1 2 W sin cos correct Explanation: Analyzing the torques on the bar, with the hinge at the axis of rotation, summationdisplay = LT parenleftbigg L 2 sin parenrightbigg W = 0 T = 1 2 W sin . Analyzing horizontal equilibrium on the bar, summationdisplay F x = H x T cos = 0 H x 1 2 W sin cos = 0 H x = 1 2 W sin cos . 002 (part 1 of 3) 10.0 points A 1347 N uniform boom of length is sup ported by a cable, as shown. The boom is pivoted at the bottom, the cable is attached a distance 3 4 from the pivot, and a 4922 N weight hangs from the booms top. F T 4922 N 32 58 Find the force F T applied by the supporting cable. Correct answer: 3953 . 55 N. Explanation: Let : W b = 1347 N , W m = 4922 N , b = 58 , and t = 32 . Applying the second (rotational) condition of equilibrium (with axis of rotation at the base of the beam and beam length ), alexander (jra2623) oldhomework 23 Turner (92510) 2 net = F T parenleftbigg 3 4 parenrightbigg W b parenleftbigg 2 parenrightbigg cos b W m cos b = 0 . 3 F T 2 W b cos b 4 W m cos b = 0 F T = (2 W b + 4 W m ) cos b 3 = [2 (1347 N) + 4 (4922 N)]cos 58 3 = 3953 . 55 N ....
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 Summer '08
 Kaplunovsky
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