1. A prybar is used

to remove a nail as

shown. Determine

the moment of the

240 N force about

the point O of

contact between

the prybar and the

small support block.

2. Calculate the moment Mo of the 250 N

force about the base point O of the robot.

3. The spring loaded follower A bears against the circular portion of the cam until the lobe of the cam lifts the plunger. The force required to lift the plunger is proportional to its vertical movement h from its lowest position. For design purposes, determine the angle q for which the moment of the contact force on the cam about the bearing at O is a maximum.

In the exploded view of the contact, neglect the small distance between the actual contact point B and the end C of the lobe.

4. The hydraulic cylinder AB exerts a force F of constant

magnitude 2.5 kN directed from A to B as the engine is

elevated. Determine the moment of F about the point C as a

function of q for the range 0≤ q ≤90o.

W

What is the weight W of the

engine if the combined moment

about C of the force F and

weight W for q =30o is equal to

zero?

5. The pipe assembly is

subjected to an 80 N

force. Determine the

moment of this force

about point A.

6. A 5 N vertical force is applied to the knob of the

window-opener mechanism when the crank BC is

horizontal. Determine the moment of the force about

point A and about line AB.

7. In opening a door which is equipped with a heavy-duty return mechanism, a person exerts a force of magnitude 32 N as shown. Force and the normal n to the face of the door lie in a vertical plane. Compute the moment of about the z axis.

P

P

P

30o

20o 45o 50o

45o

150 mm

A C

D

z

x

y

8. The arms AB and BC of a desk lamp lie in a vertical plane that forms an angle of

30o with xy plane. To reposition the light, a force of magnitude 8 N is applied as

shown. Determine,

a) the moment of the force about point A,

b) the moment of the force about the axis of arm AB,

Direction CD is parallel to the z-axis

and lies in a parallel plane to the

horizontal plane.

mmBCmmAB 325,450

9. Concentrated force is acting perpendicular to the

crank arm BC at point C. For the position q=70°, what is

Mx , the moment of about the x axis? At this instant,

My =-20 N·m and Mz =-37.5 N·m.

150 mm z

x

200 mm

A q

100 mm

B f

O

y

C

P

P

10. Rectangular plate

ADCF is held in

equilibrium by string

AB which has a tension

of T=14 kN.

Determine,

a) The magnitude of

the moment of about

the axis DC,

b) The perpendicular

distance between lines

AB and DC.

z

x

y

A (0, 5, 3) m

E (0, 2, 2)

C (4, 6, 0) m

B (6, 3, 0) m

F

D

O

z

x

y

A (0, 5, 3) m

E (0, 2, 2)

C (4, 6, 0) m

B (6, 3, 0) m

F D

O kjikji

n

nnnkjiT

kjinTT

DC

AFECDC

T

3

1

3

2

3

2

6

244

6412

7

32641

a)

m kN..- M

kjikjinMM

kji

kjijiTrM

M

DC

DCCDC

CBC

DC

6710339812

3

128

3

212

3

218

3

1

3

2

3

2 281218

281218

641232

?

/

z

x

y

A (0, 5, 3) m

E (0, 2, 2)

C (4, 6, 0) m

B (6, 3, 0) m

F D

O

b)

67.58

52.042

22cos ,cos)1(14

3

22

3

22

3

16

3

24

3

212

cos

3

22 , 6412

q

qq

qDCDC

DC

nTnT

kjinkjiT

The parallel component of a force to a line does not

generate moment with respect to that line. If is resolved

into two components parallel and normal to line DC, then

T

mθT

MθTM DC

DC 89.067.58sin14

67.10

sind , dsin

The magnitude of moment MDC is equal to the normal component of to line DC

and the perpendicular distance between and line DC.

T

T