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Unformatted text preview: SOME EXAM 2
PRACTICE PROBLEMS Statics Exam 2 Study Topics CHAPTER 3 Know: difference between resultant rigid~body problem and equilibrium rigidbody problem
the equations associated with each type problem the terminology of force system reductions, equivalency of systems, etc. when a system of forces and couples can be reduced to a single equivalent force at a speciﬁc location ***}+ Be able to: ’1‘ identify couples in its two forms * set up equivalent force/couple systems at speciﬁc locations
* ﬁnd the line—of—action of the resultant force where M=O 4‘ draw sketches of equivalent systems CHAPTER 4
Know: * the reactions for 2D and 3D supports * the types of constraint conditions: completely, partially, overly, improperly
* when a problem is statically indeterminate or determinate and why * how to make an improper support proper and SD * what constitutes equilibrium conditions for a 2force and 3—force body Be able to: * draw proper FBD’S of rigid bodies 4‘ draw reactions of simple supports not shown in text (i.e. “eyebolt”, “rings”, etc.) * use appropriate equilibrium equations for the solution of problems: 
in 3D use all necessary equilibrium equations when required to ﬁnd several
unknowns, and use 1 key equation when required to ﬁnd only one unknown * get the l.o.a. of the reaction of a pin support on a 2—force member (and show it in FED) ' * 301er for unknown reactions from any 2D or 3D support shown in tables even if no hwk was assigned with that particular support © STATECS GRADING RUBREC Objective Mastery Mastery Average lm prove M—— '
"—
“Ml— a]! forcesimoments with proper labels fer unknowns —
I’M_—
‘—
__. Recognizing
Pertinent
Concepts —_
_ dirvs plane reference angles ‘_ F members at a support ‘ a. i tr". ; _
f ' ' I": 'Ifi’ll if _’i'
“a couie shown as 2 parailel equal and a . osite forces _ {l' I
" 4y i' .
’\ is ‘ributed lea s to cancetrat  loads 7
5" "1 , . . direction and shape of water forces as distributed Iead I
— direction of friction forces and magnitude of normai forces 7 Process ——__ identify type of probiem: resultant or equiiibrium, 2D or 30 _ categorize force system: concurrent or noncomurrent 7‘. ‘qg‘ required to be found examples: ' ! must use anoher valid method or indeendent equation(s) to prove I I '
initial answer correct
Legibmw . ._ ——_— neat, clean paper, no erasure smudges aegmswrmngnm ._ . .. ,7 ' w 2601b
2.51m. ‘( Replace the 260—1b force
shown by an equivalent forceucouple system at C. & Problem 3.73
VECTOR MECHANICS FOR ENGINEERS ﬁle STA“CS  Page 93 'Replace the 150+N
force by an equivalent
force—couple system
at A. Mg: ‘1'" .22,é X’— Ai‘im 3%,; ﬁgmy; CE 2450 STATICS SUPPORT CONDITIONS/FBD’S For the two ﬁ‘ames Shown: 180 mm 120 mm State the force system we’re dealing with:
Describe the support conditions:
Type of supports and if SD or SI: 1)_— .2) Draw of each one. 1) " ‘ 2) Number of unknowns: _
1) List: ' 2) List: Numb er of equations: _1)__n__nm_ . 2) Write out the equations and solve if, staticain determinate with the information from
chapter 4; starting with the most efﬁcient (one unknown in one equation); SOLVENG FOR REACTIONS BY RECOGINIZING Z—FORCE MEMBERS M3. Q (1») 24%? 5254 (T)
B: @3170
E), 246:5on Cr)
3 ’5 397A} VS}?! 1 °
(:2) a=30°, (5) 3:60”. 7 ' CZ) my“ 39‘. (lg/AW
@ CL: 270 g) 5&3” gate,0
' @ 3:58an igﬂgo
D: wag USING YOUR KNOWLEDGE OF CONCWRENTINONCONCURRENT FORCE
SYSTEMS TO SOLVE FOR REACTIONS The boom derrick supports a suspended 15kjp load. :’ ﬁg 5 I K
5 The booms BC and DE are each 20 ft long. The distances are a =15ftandb= 21°Land_th_eanglcl9 = 30°.Détermine the I
tension in cable AB and the reacrjons at the pin supports C and R; C 7 '" .g‘f' k f CE 2450 STATICS PRACTICE 1N CONCEPTS FROM CHAPTER 4: A) For each structure Shown, identify members that can be classiﬁed as twoforce
elements and members that can be ciassiﬁed as threeforce'elements. Consider a the weight of the members as negligibie. (a) The mass of each box suspended from this pinconnected frame in (a)
Figure 7.1%: is 80 kg. ' ' (b) The lever system shown in Figure 7.17!) is used to support a load at end A. (c) The toggle clamp in Figure 7.170 holds the workpiece at’F. (:1) Members AB and BC in Figure 7.17.21 are pinned to (me anoﬂmr at B. ' {e} Pipe strut BC in Figure 7.17e loaded and supported as shown B) In the following probiemsr and associated ﬁgures, the FBD of that system is. A
shown. Determine if it is correct. Ifnot correct, describe what is incorrect and rediaw‘the FED correctly.
e. A curved beam of weight W is supported at A by b. A beam is pinned at B and rests against a smooth
3. p111 connecnon and at B by a rocker, as shown in incline at A as shown in E6.2.1b. The total weight of the
E6.2.1a. ‘ beam is W.
E
i
‘n
r
_E
i
t
A;
1
I %
E5_2_1a “WW age c. A forklift is lifting a crate of weight W1 as shown in E6.2.1c. The weight of the forklift is W2. The front wheels d A “While. hangs fmm the ceiling from a cord
are free to turn and the rear wheels are locked. (E‘slid} , b. A crankshaft is supported by a jOumaI hearing at B a. A_sign of weight W (500 N) with center of gravity as and a thrust bearing at D. Ignore the weight of the crank
shown is supported by cables and a collar joint (E6.3.1a). . (E6315). 7 
, . (b)
(a) z Proposed freequydiagmm , m E6.3.1 roposed reeabody diagram 0. A puliey is used to lift a weight W. The shaft of the d. A pole is ﬁxed at B and tethered by 3 mpg: as
pulley is supported by a journai bearing, as shown. Ignore shown. Ignore the WBigh’f 0f the P0Ila (E6315)
the weights of the puliey and the shaft (E6.3.1c). (d)
' J’
(C) r A {5, 6,1) m Proposed ﬂeebody diagram ' . ' '
_ ‘ Proposed freebody diagram 4.28 For the ﬂame and loading shown, determine the reactions at A andEwhen (a)a=30°.(b)a=45°. 20th  * 3:495 —@N w . 7w Wye/wer IN WoeEWW .2 3W2 MW 'iuwtwwiuobmw
ﬂag Joﬁ,
4.39 A m e bracket is held at rest by a cable attached at E an frictionless rollers. Knowing that the width ofpost F6 is sﬁghitlz less tha
distance between the rollers. determine the force exerte on ‘2: post by mﬂer when a = 20°; t 4.40 _Solye Prob. 4.39.when a f 30". 4.29 Neglecting friction, determine the tension in cable ABD and the radian at support C. g ,. 4.35 Determine due tension in each cable and the reaction at D. SOON L100 mmrim mm . Fig. 94.35 103 minJ h: 4.43 An (Elkg mas can .. supported in the three wereat wage
shown. Knowing that the pulleys have a IUDmm radius,deterrrﬁne the reac tion at A in each case.  4.95 A 250 X 400mm of mass 12 kg and a SODmm—diameter
Euﬂgx awed to axle AC which is supported by bearings at A and B. For
B = 30 , aetennine (a) the tension in the cable. {5) the reactions at A and B. (game that the — erg—does not exectao; ' DRAW FBI) ONLY. .330 NOT SOLVE.
Q _ 7 @ Member ABC—is supported by a pin maxi breakt atE
and by an inertexm'hle cord attached atA and C and passing over a ﬁction
Iess pulley at D. The tension may be assumed to be the same in Porﬁczs AD
and CD ofthe cord. For the Ioadingshawn and neglecting the size eithe
puﬂey, determine the tension in the cbrd and the reaeﬁon at 3. Determine the reactions at A andB when 5 = 80’. Fig. P435 ©' All S—Izg siender rod oflength L is attached to collars wiﬁch may
Slide freeiy along, the guides shown Knowing that the rod is in equilibrium
and that ﬂ = 30’, determine (a) the angle 3 that the rod forms with the
vertical, (b) the reactidns at A and B. _ _ 1 I i
7' Three rods are welded together to form a “coma” which is supported by three eyebolts, Neglecting friction. ﬁeterrm'ne the at
A, B, and then P=240Ib, a= 12m.,b=8in..a.ndc= 10in. F19 154.34 _ A ﬁlokg cover for a roof opening is hinged at comers A and B;
The roof forms an angle of 30° with the horizontal, and the cover is main 7
'tained in a horizontal pasition by the brace CE. Determine (a) the magnitude
afthe force exerted by the brace, (In) the reactions at the hinges. Assume that
the hiﬁge at A does not exert any axial thrust. E Fig. P4114 Anf—kgmmmbempportedinthediﬁ'mtways
' I shown. Knowingthepuﬂeys have: 10011111: radius,
dderminethcrucﬁonsincachcase. ' 5.151 Two shafs AC and CF, which lie in the vertical :y pins, are
connected a universal joint at C. The bearings at B and D do not enter: any
2an force. A couple of magnitude 500 lb (clockwise when viewed from
the positive: axis) is applied to shaft CF31 1". At a time when the arm of the
cmsspieee attached to shaft CF is hoﬁzonml, determine (a) the'magnimde of
the muple which must be applied to shaft AC at A to equilibrium.
(5} the reactions at B, D, and E. (Hint The sum of the couple's exerted on the Wicca mustbe zero.) W FED. C13 53¢“ 3W7: {c} CE 2450 STATICS QUIZ 3 ' NAME: DIRECTIONS: SHOW ALL WORK FOR FULL CREDIT 20 PTS
10 MNUTES The bent rod ABEF is supported by beatings at C and D and by wire AH. The portion of the rod
AB is 250 mm long and the hearing at D does not exert any axial thrust. A) Draw the correct FED. B) Write the one eguatien needed to directly solve for the force in the wire AH. BEER a. JOHNSTON ‘ _ ' Problem 4.95
VECTOR MECHANICS FOR ENGINEERS 5/e . STAT'CS Page 162
Plumber exerts at A: _P_‘=—(6.51b)j_
g=—(97.51bft)1 Determine reactions
at B, C, and'D caused
by the plumber, ' BEER & JOHNSTON Problem 4.101
VECTOR MECHANICS FOR ENGINEERS 5/6 Page 163 Rod ABC is hinged to a
vertical wall and bears at C against another
vertical wall. For the
load P2215ON, find the
reaction at C. (Neglect
friction.) Mi 5‘. Team. 2
Mia: (63,4 1M“?
Myé: «409; t} lbsH; (25 points) A 4ft long bar AC is supported by a hinge at A and the cable BD. The hinge axis
is along the z—axis; The centerline of the bar lies in the x—y plane, and the cable attachment '
point, B, is the midpoint of the bar. Determine the magnitude and direction of the reaction
moments exerted on the bar by the single hinge at A. y Category of force system:
Type of problem;
# of unknowns:_
# of available eqns:
# of unknowns required to ﬁnd;
Write the necessary equations in order of greatest
efficiency.
Given info: A( 0, 0, O)
B(200s30, —l, 0) ﬁ
C(4cos30, —2, O)
D( 2, 2, ~l) —100j (1b) '6
_._..———s . .' r"  . . _ . 7
m0#.....—. ...._.__..._‘..._ CE 2450 77"7  ' “EXAM 2_—. TIME:‘1 HOUR
Problem#1 (33%) ‘ _ , _ . _ __ ‘ ' A2D ﬁameisloadedasshown. Itissupporrtedbye
" ﬁxede'naatAo. _' 7 """" " " "
1 Draw' a clear Ftee Body Diagram of the frame I
showingallthe'detaﬂs. ‘ . ' 3  tionsatA. ! Problem # 2 ( 30 0/0 ' " A uniform pipeoover ofrladius 9 in. and weight60
lbs. is held in a. horizontal position by cable CD. Assuming that the hearing at B does not exert
m axial thrust, determine _ 1 Thetensiozzinthe cable. ‘T: 70%
DEAN A CLEAR Fab MGM a ’ i
goutamass (33%) gcéélgléfj :5: 74b} Z3 :: 553%
The building is to fout'parallel coiumn loads es ShoWﬁ. : . 7 Y 
Given that the Resultant Force Couple System at the Origin is: _ mm _ ' __  r; 3'4: = — mock kNm waif(5'63 kN, \._ ‘ Q) Determine the magnitudes of the forces F1 , F; , and Fa.~ _1551fé33}¢m#4 (47o)    The structures not statically determinate.
1 Describe one modiﬁcation in the supports in each case
_. that would make the structure statically determinate.
 _ . bot“ _‘ [m3 __ . _:.  1".‘7 , ...
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