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(a) Draw the free body diagram of the bar.
(b) Determine the reactions at the builtin support at A.
SOLUTION:
(a) The free body diagram of the bar
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i 200 lb
600 €tLb *
.h; i
120 I ' l i g 1
”O, i . I I i 4 In:
E r. l 175314 I I x
“—3 I 5 Ft—I (b) Determine the reactions at the builtin support, A. Because two unknown force components exist at point A. the solution is simplified by ﬁrst summing moments there. = O =  600 ftIb  (200 b)(cos 30°)(4 ft) 4 (120 b)(sin 30°)(5 ft)  MA ANS MA = 167.2 ft—tb clockwise Summing forces in the x and ydirections:
2F, = 0 = (200 ib)(cos 30°)  A,
ANS Ax = 173.2 lb <— zF, = 0 = (200 lb)(sin 30°)  120 lb + A,
ANS Ay = 20 lb T PROBLEM 13.4 In Problem 1.3.3, suppose that you want to change the 5ft
dimension so that the couple exerted on the beam by the
builtin support is zero. What is the required dimension? SOLUTION: i'.
Free body diagram: j 200 Lb
600 F‘tlo a 3/
\ i r I I Wﬂgr
i i l 3
0 u "i ‘ :
Fae \' I I I 'i f‘
1 ; K Summing moments about point B in order to determine the distance, d: 2MB" — o —  600 ft—lb + (100 lb) (8 it) + (200 lb) (sin 30°) (d) (200 lb) (4 n) (cos 30°) ANS d= 3.33ft A...»..._...‘.......Lm w ...
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 Spring '06
 Keil

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