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PROBLEM 8.114
Solve Problem 8.113 assuming that the belt is looped
around the pulleys in a figure eight.
PROBLEM 8.113
A flat belt is used to transmit a couple
from pulley A to pulley B. The radius of each pulley is 60
mm, and a force of magnitude P 900 N is applied as
shown to the axle of pulley A. Knowing that the coefficient
of static friction is 0.35, determine (a) the largest couple
that can be transmitted, (b) the corresponding maximum
value of the tension in the belt.
PROBLEM 8.115
The speed of the brake drum shown is controlled by a belt attached to the
control bar AD. A force
P
of magnitude 25 lb is applied to the control bar
at A. Determine the magnitude of the couple being applied to the drum,
knowing that the coefficient of kinetic friction between the belt and the
drum is 0.25, that a 4 in., and that the drum is rotating at a constant
speed (a) counterclockwise, (b) clockwise.
PROBLEM 8.115 (Continued)
PROBLEM 8.116
The speed of the brake drum shown is controlled by a belt attached to the
control bar AD. Knowing that a 4 in., determine the maximum value of
the coefficient of static friction for which the brake is not self-locking
when the drum rotates counterclockwise.
PROBLEM 8.117
The speed of the brake drum shown is controlled by a belt attached to the
control bar AD. Knowing that the coefficient of static friction is 0.30 and
that the brake drum is rotating counterclockwise, determine the minimum
value of a for which the brake is not self-locking.
PROBLEM 8.118
Bucket A and block C are connected by a cable that passes over drum B.
Knowing that drum B rotates slowly counterclockwise and that the
coefficients of friction at all surfaces are
s
0.35 and
k
0.25,
determine the smallest combined mass m of the bucket and its contents
for which block C will (a) remain at rest, (b) start moving up the incline,
(c) continue moving up the incline at a constant speed.
PROBLEM 8.118 (Continued)
PROBLEM 8.119
Solve Problem 8.118 assuming that drum B is frozen and cannot rotate.
PROBLEM 8.118
Bucket A and block C are connected by a cable that
passes over drum B. Knowing that drum B rotates slowly
counterclockwise and that the coefficients of friction at all surfaces are
0.35
s
and
0.25,
k
determine the smallest combined mass m of
the bucket and its contents for which block C will (a) remain at rest,
(b) start moving up the incline, (c) continue moving up the incline at a
constant speed.
1
0.35(2/3 )
1
1
2.0814
0.48045
T
mg e
T
mg
T
mg
PROBLEM 8.119 (Continued)
PROBLEM 8.120
A cable is placed around three parallel pipes. Knowing that the
coefficients of friction are
0.25
s
and
0.20,
k
determine
(a) the smallest weight W for which equilibrium is maintained,
(b) the largest weight W that can be raised if pipe B is slowly
rotated counterclockwise while pipes A and C remain fixed.
