PROBLEM 3-53 (page 100, 12th edition) . Determine the force acting along the axis of each of the three struts needed to hold the 500 kg block in equilibrium. Z. D B 2.5 m 2 m x 3 m 1.25 m 0.75 m y PROB03_53.jpg Copyright @ 2010 Pearson Prentice Hall, Inc.
PROBLEM 3-53 (page 100, 12th edition) COORDINATES 2 1 1 D ( - 1 , 25 , - 2, 0 ) mg - . 1 1 1 1 1 - - - 6 1 0.75 , - 2,07 m 1 2 B/0, 0,0 m . A (0,3 , 2, 5 ) m 1 1 1 1 5 - y
3-53 (page 110, 12th edition) COMPLETION OF PROBLEM (page 1) · Forces (suppressing units) FRA= (3j + 2.5k) X F AC = (0.75 i ! 5 j ! 2.5 k) Y ! ! X=F. / v32 +2.52 Y=F/ v0.752 +52 +2.52 ! ! F AD = (!1.25 i ! 5 j ! 2.5 k) Z F block =! 500(9.81) k Z = F / 1.252 +52 +2.52 · Equations of equilibrium ! F =F i+F ! „j+F k = 0 R "Rx Ry Rz F =! F =0: 0.75Y !1.25Z=0 Rx `xx F =! F =0: Ry yy 3X!5Y!5Z =0 F =F =0: Rz Z 2.5X! 2.5Y +2.5Z! 500(9.81) = 0 · Solving X = 4905 Y=1839 Z=1104 FRA =19.2 kN F =10.4 kN AD Fan= 6.32 kN `BA AC