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PROBLEM 8.15
A uniform crate with a massof 30 kg must be moved up along the 15°
incline without tipping. Knowing that force
P
is horizontal, determine
(a) the largest allowable coefficient of static friction between the crate and
the incline, (b) the corresponding magnitude of force
P
.
PROBLEM 8.15 (Continued)
PROBLEM 8.16
A worker slowly moves a 50-kg crate to the left along a loading dock
by applying a force
P
at corner B as shown. Knowing that the crate
starts to tip about the edge E of the loading dock when a 200 mm,
determine (a) the coefficient of kinetic friction between the crate and
the loading dock, (b) the corresponding magnitude P of the force.
PROBLEM 8.17
A half-section of pipe weighing 200 lb is pulled by a cable as
shown. The coefficient of static friction between the pipe and the
floor is 0.40. If α = 30°, determine (a) the tension T required to
move the pipe, (b) whether the pipe will slide or tip.
PROBLEM 8.18
A 120-lb cabinet is mounted on casters that can be locked to prevent their
rotation. The coefficient of static friction between the floor and each caster
is 0.30. Assuming that the casters at both A and B are locked, determine
(a) the force
P
required to move the cabinet to the right, (b) the largest
allowable value of h if the cabinet is not to tip over.
PROBLEM 8.19
Wire is being drawn at a constant rate from a spool by applying a vertical
force
P
to the wire as shown. The spool and the wire wrapped on the spool
have a combined weight of 20 lb. Knowing that the coefficients of friction at
both A and B are
s
0.40 and
k
0.30, determine the required magnitude
of the force
P
.
PROBLEM 8.20
Solve Problem 8.19 assuming that the coefficients of friction at B are zero.
PROBLEM 8.19
Wire is being drawn at a constant rate from a spool by
applying a vertical force
P
to the wire as shown. The spool and the wire
wrapped on the spool have a combined weight of 20 lb. Knowing that the
coefficients of friction at both A and B are
s
0.40 and
k
0.30, determine
the required magnitude of the force
P
.
PROBLEM 8.21
The cylinder shown is of weight W and radius r. Express in terms W and r the
magnitude of the largest couple
M
that can be applied to the cylinder if it is not to
rotate, assuming the coefficient of static friction to be (a) zero at A and 0.30 at B,
(b) 0.25 at A and 0.30 at B.
PROBLEM 8.22
The cylinder shown is of weight W and radius r, and the coefficient of static
friction
s
is the same at A and B. Determine the magnitude of the largest couple
M
that can be applied to the cylinder if it is not to rotate.
PROBLEM 8.23
End A of a slender, uniform rod of length L and weight W bears on a
surface as shown, while end B is supported by a cord BC. Knowing that
the coefficients of friction are
0.40
s
and
0.30,
k
determine (a) the
largest value of
for which motion is impending, (b) the corresponding
value of the tension in the cord.
