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PROBLEM 8.104
A hawser is wrapped two full turns around a bollard. By exerting an 80-lb force on the free end of the
hawser, a dockworker can resist a force of 5000 lb on the other end of the hawser. Determine (a) the
coefficient of static friction between the hawser and the bollard, (b) the number of times the hawser
should be wrapped around the bollard if a 20,000-lb force is to be resisted by the same 80-lb force.
PROBLEM 8.105
Two cylinders are connected by a rope that passes over two fixed rods as
shown. Knowing that the coefficient of static friction between the rope
and the rods is 0.40, determine the range of the mass m of cylinder D for
which equilibrium is maintained.
PROBLEM 8.106
Two cylinders are connected by a rope that passes over two fixed rods as
shown. Knowing that for cylinder D upward motion impends when
m = 20 kg, determine (a) the coefficient of static friction between the rope
and the rods, (b) the corresponding tension in portion BC of the rope.
PROBLEM 8.107
Knowing that the coefficient of static friction is 0.25 between the rope and the
horizontal pipe and 0.20 between the rope and the vertical pipe, determine the
range of values of P for which equilibrium is maintained.
PROBLEM 8.108
Knowing that the coefficient of static friction is 0.30 between the rope and the
horizontal pipe and that the smallest value of P for which equilibrium is
maintained is 80 N, determine (a) the largest value of P for which equilibrium
is maintained, (b) the coefficient of static friction between the rope and the
vertical pipe.
PROBLEM 8.109
A band belt is used to control the speed of a flywheel as shown.
Determine the magnitude of the couple being applied to the
flywheel, knowing that the coefficient of kinetic friction between
the belt and the flywheel is 0.25 and that the flywheel is rotating
clockwise at a constant speed. Show that the same result is
obtained if the flywheel rotates counterclockwise.
PROBLEM 8.110
The setup shown is used to measure the output of a small turbine. When the
flywheel is at rest, the reading of each spring scale is 14 lb. If a 105-lb · in.
couple must be applied to the flywheel to keep it rotating clockwise at
a constant speed, determine (a) the reading of each scale at that time, (b) the
coefficient of kinetic friction. Assume that the length of the belt does not
change.
PROBLEM 8.111
The setup shown is used to measure the output of a small turbine. The
coefficient of kinetic friction is 0.20 and the reading of each spring scale is
16 lb when the flywheel is at rest. Determine (a) the reading of each scale
when the flywheel is rotating clockwise at a constant speed, (b) the couple
that must be applied to the flywheel. Assume that the length of the belt does
not change.
PROBLEM 8.112
A flat belt is used to transmit a couple from drum B to drum A. Knowing
that the coefficient of static friction is 0.40 and that the allowable belt
tension is 450 N, determine the largest couple that can be exerted on drum A.
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.
