Solutions Manual
Engineering Mechanics: Statics
2nd Edition
Statics 2e 3
Important Information about
4Solutions Manual
Accuracy of Numbers in Calculations
Statics 2e 267
Chapter 3 Solutions
Problem 3.1
Consider an airplane whose motion is described below. For each case, state whether or not the airplane is
in static equilibrium, with a brief explanation.
(a) The airplane flies in a straight line at a constant speed and at a constant altitude.
(b) The airplane flies in a straight line at a constant speed while climbing in altitude.
(c) The airplane flies at a constant speed and at a constant altitude while making a circular turn.
(d)
After touching down on the runway during landing, the airplane rolls in a straight line at a constant
speed.
(e)
After touching down on the runway during landing, the airplane rolls in a straight line while its
brakes are applied to reduce its speed.
Note: Concept problems are about explanations, not computations.
Problem 3.2
The structure shown uses members
AB
,
BC
, and
BD
to support an object with
the weight or mass given in the figure. Determine the force supported by each of
these members, indicating whether they are in tension or compression.
Problem 3.3
The structure shown uses members
AB
,
BC
, and
BD
to support an object with the
weight or mass given in the figure. Determine the force supported by each of these
members, indicating whether they are in tension or compression.
Problem 3.4
The structure shown uses members
AB
,
BC
, and
BD
to support an object with the
weight or mass given in the figure. Determine the force supported by each of these
members, indicating whether they are in tension or compression.
Solution
Problem 3.5
The structure shown uses members
AB
,
BC
, and
BD
to support an object with
the weight or mass given in the figure. Determine the force supported by each
of these members, indicating whether they are in tension or compression.
Problem 3.6
In Fig. P3.2, determine what the 20
ı
orientation of member
BC
should be changed to (i.e., determine
angle
˛
) so that the force this member supports is as small as possible, and determine the force supported
by members AB,BC , and BD.
Problem 3.7
In Fig. P3.5, determine what the 65
ı
orientation of member
BC
should be changed to (i.e., determine
angle
ˇ
) so that the force this member supports is as small as possible, and determine the force supported
by members AB,BC , and BD.
Problem 3.8
In a machining setup, workpiece
B
, which weighs
20 lb
, is supported by a fixed
V block
E
and a clamp at
A
. All contact surfaces are frictionless, and the clamp
applies a vertical force of
35 lb
to the workpiece. Determine the reactions at points
Cand Dbetween the V block and the workpiece.
Problem 3.9
In a machining setup, workpiece
B
, which weighs
20 lb
, is supported by a fixed
V block
E
and a clamp at
A
. All contact surfaces are frictionless, and the clamp
applies a vertical force of
35 lb
to the workpiece. Determine the reactions at
points Cand Dbetween the V block and the workpiece.
Problem 3.10
A skier uses a taut tow rope to reach the top of a ski hill. The skier weighs
150 lb
, the snow-covered slope is frictionless, and the tow rope is parallel to the
slope.
(a)
If
T2D200 lb
, determine the value of
T1
to move the skier up the slope
at constant velocity and the reaction between the skier and the slope.
(b)
If
T1D200 lb
, determine the value of
T2
to move the skier up the slope
at constant velocity and the reaction between the skier and the slope.
Problem 3.11
The dimension
h
is to be determined so that a worker can comfortably slide
boxes weighing up to
100 lb
up and down a frictionless incline. If the worker
can apply to the box a
50 lb
horizontal force (parallel to the ground), determine
the largest value hmay have.
Problem 3.12
Blocks Aand Beach have 5kg mass, and all contact surfaces are frictionless.
(a)
Determine the force
F
needed to keep the blocks in static equilibrium and the
forces on all contact surfaces.
(b)
If the value of
F
determined in Part (a) is applied, will the blocks move?
Explain.
(c) If Fis smaller than the value determined in Part (a), describe what happens.
Problem 3.13
Bead Ahas 2kg mass and slides without friction on bar BC .
(a)
Determine the force
F
needed to keep the bead in static equilibrium and
the reaction force between the bead and bar.
(b)
If the value of
F
determined in Part (a) is applied, will the bead move?
Explain.
(c)
If
F
is larger than the value determined in Part (a), describe what happens.
Problem 3.14
A crane is used to lift a concrete pipe weighing
5kN
into place. If
dD
0:25 m, determine the tension in cables AB and AC .
Problem 3.15
A crane is used to lift a concrete pipe weighing
5kN
into place. For precision
positioning, the worker at
C
can apply up to a
400
N force to cable
AC
.
Determine the largest distance dthe concrete pipe may be moved.
Problem 3.16
Guy wire
AB
is used to help support the utility pole
AC
. Assuming the force
supported by the utility pole is directed along the line
AC
, determine the force
in wire AB and pole AC if PD800 N.