COSMOS: Complete Online Solutions Manual Organization System
Chapter 8, Solution 1. FBD Block B: Tension in cord is equal to W A = 25 lb from FBD’s of block A and pulley. ΣFy = 0:
N − WB cos 30° = 0,
N = WB cos 30°
(a) For smallest WB , slip impends up the incline, and
F = µ s N = 0.35WB cos30° ΣFx = 0:
F − 25 lb + WB sin 30° = 0
( 0.35cos30° + sin 30° )WB = 25 lb WB min = 31.1 lb (b) For largest WB , slip impends down the incline, and F = − µ s N = − 0.35 WB cos30° ΣFx = 0:
Fs + WB sin 30° − 25 lb = 0
( sin 30° − 0.35cos30° )WB = 25 lb W B max = 127.0 lb
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.