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PROBLEM 12.36
A 450-g tetherball A is moving along a horizontal circular path at a
constant speed of 4 m/s. Determine (a) the angle
that the cord
forms with pole BC, (b) the tension in the cord.
PROBLEM 12.37
During a hammer thrower’s practice swings, the 7.1-kg head
A of the hammer revolves at a constant speed v in a horizontal
circle as shown. If 0.93 m
and
60 ,
determine
(a) the tension in wire BC, (b) the speed of the hammer’s
head.
PROBLEM 12.38
Human centrifuges are often used to simulate different acceleration
levels for pilots. When aerospace physiologists say that a pilot is
pulling 9g’s, they mean that the resultant normal force on the pilot from
the bottom of the seat is nine times their weight. Knowing that the
centrifuge starts from rest and has a constant angular acceleration of
1.5 RPM per second until the pilot is pulling 9g’s and then continues
with a constant angular velocity, determine (a) how long it will take for
the pilot to reach 9g’s (b) the angle of the normal force once the pilot
reaches 9 g’s. Assume that the force parallel to the seat is zero.
PROBLEM 12.39
A single wire ACB passes through a ring at C attached to a sphere which
revolves at a constant speed v in the horizontal circle shown. Knowing that
the tension is the same in both portions of the wire, determine the speed v.
PROBLEM 12.40*
Two wires AC and BC are tied at C to a sphere which revolves at a
constant speed v in the horizontal circle shown. Determine the range of
the allowable values of v if both wires are to remain taut and if the
tension in either of the wires is not to exceed 60 N.
PROBLEM 12.40* (Continued)
PROBLEM 12.41
A 1-kg sphere is at rest relative to a parabolic dish which rotates at a
constant rate about a vertical axis. Neglecting friction and knowing
that r
1 m, determine (a) the speed v of the sphere, (b) the
magnitude of the normal force exerted by the sphere on the inclined
surface of the dish.
PROBLEM 12.42*
As part of an outdoor display, a 12-lb model C of the earth is attached to wires AC and
BC and revolves at a constant speed v in the horizontal circle shown. Determine the
range of the allowable values of v if both wires are to remain taut and if the tension in
either of the wires is not to exceed 26 lb.
PROBLEM 12.42* (Continued)
PROBLEM 12.43*
The 1.2-lb flyballs of a centrifugal governor revolve at a constant speed v
in the horizontal circle of 6-in. radius shown. Neglecting the weights of
links AB, BC, AD, and DE and requiring that the links support only tensile
forces, determine the range of the allowable values of v so that the
magnitudes of the forces in the links do not exceed 17 lb.
