homework 4

25 N.m
115 N
100 N
5. Two forces and a couple (applied to portion AB) are applied to the car’ s exhaust
system as shown. Replace the given force system with an equivalent force-couple
system at D.
* Line MN lies in a plane parallel to the horizontal plane
* Line AD lies in the xz plane and makes a 37° angle with the x axis.
6. The direction cosines of robot arm AB are cos qx=0.6, cos qy (qy <90°) and cos qz=0. For arm BC the direction
cosines are, cos qx=7/9, cos qy=4/9 and cos qz=-4/9. A force of magnitude F=250 N and a couple of magnitude C=27
Nm along the axis BC are applied to the end C of arm BC. Determine the moment about line AD. Replace the force and
couple acting on the robot assembly with an equivalent force-couple at point A.
7) Replace the system of one force and three couples with an equivalent resultant force and resultant
couple acting at point O. Then reduce the system to a wrench. Determine the coordinates of the point the
line of action of the wrench intersects the xy plane.
F = 14 N
z
C1=34 Nm (lies in plane ADE)
A (0, 0, 4) m
I

C3
C2=44 Nm (lies in plane ACD)
C3=80 Nm (lies in plane AGHI)
H
G

F
O

C2

C1
E (0, 3, 0) m
y
6m
D (3, 5, 0) m
J
B
12 m
C (6, 4, 0) m
x
8) Replace the two forces acting on the pole by a wrench. Write the
moment associated with the wrench as a vector and specify the
coordinates of the point P in the y-z plane through which the line of
action of the wrench passes.