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PROBLEM 13.18
The subway train shown is traveling at a speed of 30 mi/h when
the brakes are fully applied on the wheels of cars A, causing it
to slide on the track, but are not applied on the wheels of cars A
or B. Knowing that the coefficient of kinetic friction is 0.35
between the wheels and the track, determine (a) the distance
required to bring the train to a stop, (b) the force in each
coupling.
PROBLEM 13.19
Blocks A and B weigh 25 lbs and 10 lbs, respectively, and they are both at a
height 6 ft above the ground when the system is released from rest. Just before
hitting the ground block A is moving at a speed of 9 ft/s. Determine (a) the
amount of energy dissipated in friction by the pulley, (b) the tension in each
portion of the cord during the motion.
PROBLEM 13.19 (Continued)
PROBLEM 13.20
The system shown is at rest when a constant 30 lb force is
applied to collar B. (a) If the force acts through the entire
motion, determine the speed of collar B as it strikes the
support at C. (b) After what distance d should the 30 lb
force be removed if the collar is to reach support C with
zero velocity?
PROBLEM 13.21
Car B is towing car A at a constant speed of 10 m/s on an uphill
grade when the brakes of car A are fully applied causing all four
wheels to skid. The driver of car B does not change the throttle
setting or change gears. The masses of the cars A and B are
1400 kg and 1200 kg, respectively, and the coefficient of
kinetic friction is 0.8. Neglecting air resistance and rolling
resistance, determine (a) the distance traveled by the cars
before they come to a stop, (b) the tension in the cable.
PROBLEM 13.22
The system shown is at rest when a constant 250-N force is applied to
block A. Neglecting the masses of the pulleys and the effect of friction
in the pulleys and between block A and the horizontal surface,
determine (a) the velocity of block B after block A has moved 2 m, (b)
the tension in the cable.
PROBLEM 13.22 (Continued)
PROBLEM 13.23
The system shown is at rest when a constant 250-N force is applied to
block A. Neglecting the masses of the pulleys and the effect of friction
in the pulleys and assuming that the coefficients of friction between
block A and the horizontal surface are
0.25
s
m
=
and
0.20,
k
m
=
determine (a) the velocity of block B after block A has moved 2 m, (b)
the tension in the cable.
PROBLEM 13.23 (Continued)
PROBLEM 13.24
Two blocks A and B, of mass 4 kg and 5 kg, respectively, are connected
by a cord which passes over pulleys as shown. A 3 kg collar C is placed
on block A and the system is released from rest. After the blocks have
moved 0.9 m, collar C is removed and blocks A and B continue to move.
Determine the speed of block A just before it strikes the ground.
