University:
Michigan State University
Course:
ERG 160 | Success in Science, Technology, Engineering, and Mathematics
Academic year:

2020
Views:

470

Pages:

1
Author:

omiliar74be

COSMOS: Complete Online Solutions Manual Organization System Chapter 8, Solution 135. FBD ladder: Motion impends at both A and B, so FA = µ s N A ΣM A = 0: NB = or a W =0 2 lN B − ΣFx = 0: FA + ΣFy = 0: 2.5W 13 5 12 FB − NB = 0 13 13 NA − l = 19.5 ft a 7.5 ft W = W 2l 39 ft 2.5 W 13 µs N A + a = 7.5 ft NB = or FB = µ s N B = µ s Then a 5 = l 13 FB = µ s N B and 12.5 (13) µ sW − 30 (13)2 W =0 ( 30 − 12.5µs ) W (13) NA − W + 2 2 µs 12 5 FB + NB = 0 13 13  30 − 12.5µ s  W + 30µ s + 12.5  =W  2 µs   (13) b 12 = l 13 or µ s2 − 5.6333µ s + 1 = 0 µ s = 2.8167 ± 2.6332 or µ s = 0.1835 and µ s = 5.45 The larger value is very unlikely unless the surface is treated with some “non-skid” material. In any event, the smallest value for equilibrium is µ s = 0.1835 Vector Mechanics for Engineers: Statics and Dynamics, 8/e, Ferdinand P. Beer, E. Russell Johnston, Jr., Elliot R. Eisenberg, William E. Clausen, David Mazurek, Phillip J. Cornwell © 2007 The McGraw-Hill Companies.