1401 Review problems for Chapters 10 – 14.
1. Jeff of the Jungle swings on a vine that is 7.20 m long. At the bottom of the swing, just before
hitting the tree, Jeff’s linear speed is 8.50 m/s. (a) Find Jeff’s angular speed at this time. (b) What
centripetal acceleration does Jeff experience at the bottom of his swing? (1.18 rad/s, 10.0 m/s2.)
2. When a pitcher throws a curve ball, the ball is given a fairly rapid spin. If a 0.15-kg baseball
with a radius of 3.7 cm is thrown with a linear speed of 46 m/s and an angular speed of 41 rad/s, how
much of its kinetic energy is translational and how much is rotational? Assume the ball is a uniform, solid
sphere. 2. (Translational: 159 J, rotational: 0.0690 J.)
3. When a ceiling fan rotating with an angular speed of 2.65 rad/s is turned off, a frictional torque
of 0.12 N∙m slows it to a stop in 19.5 s. What is the moment of inertia of the fan? (0.883 kg m2.)
4. A child exerts a tangential 40.0-N force on the rim of a merry-go-round with a radius of 2.40 m.
Please calculate its torque. If the merry-go-round’ moment of inertia is 800 kg m2, what is its angular
acceleration? What is its mass? (96 Nm, 0.12 rad/s2, 278 kg.)
5. As a platter with diameter 0.250 m and mass 400 g is rotating with angular speed of 5.00 rad/s,
you put a metal bar on it so they move with common angular speed of 3.00 rad/s. Ignore all the friction,
can you tell me the moment of inertia of the metal bar? If the bar’s length is 0.200 m, can you tell me the
mass of the bar? 5. (2.08*10-3 kg m2, 0.625 kg)
6. In one hand you hold a 0.12-kg apple, in the other hand a 0.20-kg orange. They are separated by
0.75 m. What is the magnitude of the force of gravity that (a) the orange exerts on the apple and (b) the
apple exerts on the orange? (2.85*10-12 N, same.)
7. Titan is the largest moon of Saturn and the only moon in the solar system known to have a
substantial
atmosphere. Find the acceleration due to gravity on Titan’s surface, given that its mass is 1.35 ×
1023 kg and its radius is 2570 km. (1.36 m/s2)
8. (a) Calculate the potential energy of a 10.0-kg mass on the surface of the Earth and at an altitude
of 400 km respectively; (b) calculate the speed needed to move this mass from surface of the Earth to the
altitude of 400 km. (-6.25*108 J, -5.88*108 J, 2.72*103 m/s)
9. A person in a rocking chair completes 12 cycles in 24 s. What are the period and frequency of
the rocking? (2.0 s, 0.50 Hz.)
10. A 0.50-kg mass attached to a spring undergoes simple harmonic motion with a period of 0.75
s. What is the force constant of the spring? (35.1 N/m)
11. After landing on an unfamiliar planet, a space explorer constructs a simple pendulum of length
50.0 cm. The explorer finds that the pendulum completes 95.0 full swing cycles in a time of 130 s. What
is the value of the acceleration of gravity on this planet? (10.5 m/s2)
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12. A wave travels along a stretched horizontal rope. The vertical distance from crest to trough for
this wave is 11 cm and the horizontal distance from crest to trough is 26 cm. What is (a) the wavelength
and (b) the amplitude of this wave? (52 cm, 5.5 cm)
13. The intensity level in a truck is 95 dB. What is the intensity of this sound? (3.16*10-3 W/m2)
14. A train is traveling at 30.0 m/s relative to the ground in still air. The frequency of the note
emitted by the train whistle is 262 Hz. (a) What frequency f 1 is heard by you if you are standing on the
ground and the train is moving toward you? (b) If the train is not moving, but you are driving a car toward
it at 30.0 m/s relative to the ground, what frequency f 2 is heard by you? (287 Hz, 285 Hz)
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