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*Computer-Oriented Problems

*2/176 Four forces are exerted on the eyebolt as shown. If

the net effect on the bolt is a direct pull of 1200 N

in the y-direction, determine the necessary values

of Tand .

Problem 2/176

30

30

y

x

800 N

480 N

720 N

T

C ha pt er 2 F or ce Sy st em s

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*2/177 The force F is directed from A toward D and D is

allowed to move from B to C as measured by the

variable s. Consider the projection of F onto line

EFas a function of s. In particular, determine and

plot the fraction n of the magnitude F which is

projected as a function of s/d. Note that s/d variesfrom 0 to .

Ans.

Problem 2/177

*2/178 The throttle-control lever OA rotates in the range

0 90. An internal torsional return spring

exerts a restoring moment about O given by M

K( /4), where K 500 and is in

radians. Determine and plot as a function of the

tension Trequired to make the net moment about

O zero. Use the two values d 60 mm and d

160 mm and comment on the relative design mer-

its. The effects of the radius of the pulley at B are

negligible.

Problem 2/178

d

T

B

M

A

40 mm45 40 mm

O

N mm/rad

B

A

F

E

F

D

s

C d

2d2d

n

2 sd

1

5sd2

5 22 sd

22

A rt i cl e 2 /1 0 R ev i ew P ro b le m s

*2/179 With the cylindrical partP of weight 1500 N in it

grip, the robotic arm pivots about O through th

range 45 45 with the angle at A locke

at 120. Determine and plot (as a function of ) th

moment at O due to the combined effects of th

weight of part P, the 600-N weight of member OA(mass center at G1), and the 250-N weight o

member AB (mass center at G2). The end grip i

included as a part of member AB. The lengths L

and L2 are 900 mm and 600 mm, respectively

What is the maximum value of MO and at wha

value of does this maximum occur?

Ans.

Problem 2/179

A

120

BP

OG1

G2

L12

L12

L2

2

L2

2

(MO)max2480 N m at 19.90

MO1845 cos 975 cos(60) N m

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*2/182 The tension T in cable AB is maintained at a

constant value of 120 N. Determine the moment

MO of this tension about point O over the range

0 90. Plot the x-, y-, and z-components of

MO as functions of .

Problem 2/182

B

T

O

800 mm

800 mm

400 mm

A

A

z

x

y

C ha pt er 2 F or ce Sy st em s

*2/180 A motor attached to the shaft at O causes the arm

OA to rotate over the range 0 180. The un-

stretched length of the spring is 0.65 m, and it can

support both tension and compression. If the net

moment about O must be zero, determine and plot

the required motor torque Mas a function of .

Problem 2/180

*2/181 A flagpole with attached light triangular frame is

shown here for an arbitrary position during its

raising. The 75-N tension in the erecting cable re-

mains constant. Determine and plot the moment

about the pivot O of the 75-N force for the range

0 90. Determine the maximum value of

this moment and the elevation angle at which it

occurs; comment on the physical significance of

the latter. The effects of the diameter of the drum

at D may be neglected.

Ans.

Problem 2/181

D

6 m

O

A

3m

3m

3 m

B

C

(MO)max225 N m at 60

MO 1350 sin (

60

)45 36 cos (60)

kN m

O

M

B

0.5 m

x

y

A A

A

0.3 m

k = 600 N/m

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*2/183 The arm AB rotates in the range 0 180,

and the spring is unstretched when 90. De-

termine as a function of the moment about O of

the spring force as applied at B. Plot the three

scalar components of MO, and state the maximum

absolute value of each component.

Ans.

= 123.7 at 0, 180

= 61.8 at 0, 180

Problem 2/183

A

z

D

B

k= 2.6 kN/m

Ox

y

360 mm

360 mm

720 mm

C

N m(MOz)max

N m(MOx)max

MO1.5 0.5 sin 1

1.5 0.5 sin [674i337 cos k] N m

A rt i cl e 2 /1 0 R ev i ew P ro b le m s

*2/184 The rectangular plate is tilted about its lowe

edge by a cable tensioned at a constant 600 N. De

termine and plot the moment of this tensio

about the lower edge AB of the plate for the rang

0 90.

Problem 2/184

z

x

y

B

O

A

5 m

5 m

4 m

3 m

CT= 600 N