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PROPRIETARY MATERIAL. © 2013 The McGraw-Hill Companies, Inc. All rights reserved. No part of this Manual may be displayed, reproduced or distributed in any form or by any means, without the prior written permission of the publisher, or used beyond the limited distribution to teachers and educators permitted by McGraw-Hill for their individual course preparation. If you are a student using this Manual, you are using it without permission. 489 PROBLEM 12.125 A 500-lb crate B is suspended from a cable attached to a 40-lb trolley A which rides on an inclined I-beam as shown. Knowing that at the instant shown the trolley has an acceleration of 1.2 ft/s2 up and to the right, determine (a) the acceleration of B relative to A, (b) the tension in cable CD. SOLUTION (a) First we note: / ,= +B A B Aa a a where /B Aa is directed perpendicular to cable AB. : 0 cos25x B x B x B AF m a m a m aΣ = = − + ° or 2 / (1.2 ft/s )cos 25= °B Aa or 2 / 1.088 ft/s=B Aa (b) For crate B : sin 25B y B y AB B A W F m a T W a g Σ = − = ° or 2 2 (1.2 ft/s )sin 25 (500 lb) 1 32.2 ft/s 507.87 lb ABT °= + = For trolley A : sin 25 sin 25 A x A A CD AB A A W F m a T T W a g Σ = − ° − ° = or 2 2 1.2 ft/s (507.87 lb)sin 25 (40 lb) sin 25 32.2 ft/s CDT = ° + ° + or 233 lbCDT = B: A:
