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PROBLEM 12.57
A turntable A is built into a stage for use in a theatrical production.
It is observed during a rehearsal that a trunk B starts to slide on the
turntable 10 s after the turntable begins to rotate. Knowing that the
trunk undergoes a constant tangential acceleration of 0.24
2
m/s ,
determine the coefficient of static friction between the trunk and
the turntable.
PROBLEM 12.58
The carnival ride from Prob 12.51 is modified so that
the 80 kg riders can move up and down the inclined
wall as the speed of the ride increases. Assuming
that the friction between the wall and the carriage is
negligible, determine the position
h
of the rider if the
speed
v
0
= 13 m/s.
PROBLEM 12.59
The carnival ride from Prob 12.51 is modified so that
the 80 kg riders can move up and down the inclined
wall as the speed of the ride increases. Knowing that
the coefficient of static friction between the wall and
the platform is 0.2, determine the range of values of
the constant speed v
0
for which the platform will
remain in the position shown.
PROBLEM 12.59 (Continued)
PROBLEM 12.60
A semicircular slot of 10-in. radius is cut in a flat plate which rotates about
the vertical
AD
at a constant rate of 14 rad/s. A small, 0.8-lb block
E
is
designed to slide in the slot as the plate rotates. Knowing that the
coefficients of friction are 0.35
s
and 0.25,
k
determine whether
the block will slide in the slot if it is released in the position corresponding to
(
a
) 80 ,
(
b
)
40 .
Also determine the magnitude and the direction
of the friction force exerted on the block immediately after it is released.
PROBLEM 12.60 (Continued)
PROBLEM 12.60 (Continued)
PROBLEM 12.60 (Continued)
PROBLEM 12.61
A small block B fits inside a lot cut in arm OA which rotates in a vertical plane at a
constant rate. The block remains in contact with the end of the slot closest to A and
its speed is 1.4 m/s for 0150.
Knowing that the block begins to slide when
150 ,
determine the coefficient of static friction between the block and the slot.
PROBLEM 12.62
The parallel-link mechanism ABCD is used to transport a component I between manufacturing processes at
stations E, F, and G by picking it up at a station when 0
and depositing it at the next station when
180 .
Knowing that member BC remains horizontal throughout its motion and that links AB and CD rotate
at a constant rate in a vertical plane in such a way that
2.2 ft/s,
B
v
determine (a) the minimum value of the
coefficient of static friction between the component and BC if the component is not to slide on BC while being
transferred, (b) the values of
for which sliding is impending.
