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COSMOS: Complete Online <strong>Sol</strong>utions Manual Organization System<br />
Chapter 2, <strong>Sol</strong>ution 72.<br />
First replace 30 lb forces by their resultant Q:<br />
Q = 230lbcos25<br />
( ) °<br />
Q = 54.378 lb<br />
Equivalent loading at A:<br />
Law of Cosines:<br />
2 2 2<br />
( ) ( ) ( ) ( )( ) ( α) ( α)<br />
120 lb = 100 lb + 54.378 lb − 2 100 lb 54.378 lb cos 125° − cos 125° − = − 0.132685<br />
This gives two values: 125°− α = 97.625°<br />
Thus for R < 120 lb:<br />
α = 27.4°<br />
125°− α =− 97.625°<br />
α = 223°<br />
27.4°< α < 223°!<br />
Vector Mechanics for Engineers: Statics and Dynamics, 8/e, Ferdinand P. Beer, E. Russell Johnston, Jr.,<br />
Elliot R. Eisenberg, William E. Clausen, David Mazurek, Phillip J. Cornwell<br />
© 2007 The McGraw-Hill Companies.
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