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PROBLEM 12.43* (Continued)
PROBLEM 12.44
A 130-lb wrecking ball B is attached to a 45-ft-long steel cable
AB and swings in the vertical arc shown. Determine the tension
in the cable (a) at the top C of the swing, (b) at the bottom D of
the swing, where the speed of B is 13.2 ft/s.
PROBLEM 12.45
During a high-speed chase, a 2400-lb sports car traveling at a
speed of 100 mi/h just loses contact with the road as it reaches
the crest A of a hill. (a) Determine the radius of curvature
of
the vertical profile of the road at A. (b) Using the value of
found in part a, determine the force exerted on a 160-lb driver
by the seat of his 3100-lb car as the car, traveling at a constant
speed of 50 mi/h, passes through A.
PROBLEM 12.46
An airline pilot climbs to a new flight level along the path shown.
Knowing that the speed of the airplane decreases at a constant rate from
180 m/s at point A to 160 m/s at point C, determine the magnitude of the
abrupt change in the force exerted on a 90-kg passenger as the airplane
passes point B.
t
F
does not change.
N increases by 433.8 N.
magnitude of change of force
434 N
PROBLEM 12.47
The roller-coaster track shown is contained in a vertical plane.
The portion of track between A and B is straight and
horizontal, while the portions to the left of A and to the right of
B have radii of curvature as indicated. A car is traveling at a
speed of 72 km/h when the brakes are suddenly applied,
causing the wheels of the car to slide on the track
(0.20).
k
Determine the initial deceleration of the car if the brakes are
applied as the car (a) has almost reached A, (b) is traveling
between A and B, (c) has just passed B.
PROBLEM 12.47 (Continued)
PROBLEM 12.48
A spherical-cap governor is fixed to a vertical shaft that rotates with angular
velocity
. When the string-supported clapper of mass m touches the cap, a
cutoff switch is operated electrically to reduce the speed of the shaft.
Knowing that the radius of the clapper is small relative to the cap, determine
the minimum angular speed at which the cutoff switch operates.
PROBLEM 12.49
A series of small packages, each with a mass of 0.5 kg, are discharged from a
conveyor belt as shown. Knowing that the coefficient of static friction between
each package and the conveyor belt is 0.4, determine (a) the force exerted by the
belt on a package just after it has passed Point A, (b) the angle
defining the
Point B where the packages first slip relative to the belt.
PROBLEM 12.49 (Continued)
PROBLEM 12.50
A 54-kg pilot flies a jet trainer in a half vertical loop of 1200-m
radius so that the speed of the trainer decreases at a constant rate.
Knowing that the pilot’s apparent weights at Points A and C are 1680
N and 350 N, respectively, determine the force exerted on her by the
seat of the trainer when the trainer is at Point B.
