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Assignment 3
ES230
Key solutions
Problem 3.1
A 90N force is applied to the control rod
AB
as shown. Knowing that the
length of the rod is 225 mm, determine the moment of the force about
point
B
by resolving the force into components along
AB
and in a
direction perpendicular to
AB
.
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View Full Document Problem 3.5
A 2.9lb force
P
is applied to the lever which controls the auger of a
snowblower. Determine the value of
α
knowing that the moment of
P
about
A
is counterclockwise and has a magnitude of 17
lb in.
⋅
Solution 5.
By definition
/
sin
A
B A
M
r
P
θ
=
where
(
29
90
φ
=
+
° 
and
1
4.8 in.
tan
3.4 in.

=
54.689
=
°
Also
(
29
(
29
2
2
/
3.4 in.
4.8 in.
B A
r
=
+
5.8822 in.
=
Then
(
29
(
29
(
29
(
29
17 lb in.
5.8822 in. 2.9 lb sin 54.689
90
⋅
=
° +
° 
or
(
29
sin 144.689
0.99658
° 
=
or
144.689
85.260 ; 94.740
° 
=
°
°
49.9 , 59.4
∴
=
°
°
t
Problem 3.10
It is known that a force with a moment of
7840 lb in.
⋅
about
D
is required
to straighten the fence post
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This note was uploaded on 10/25/2011 for the course ENGR 2301 taught by Professor Saad during the Fall '10 term at Austin Community College.
 Fall '10
 Saad
 Statics

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