Chapter 12 Review Waves

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Chapter 12 ReviewWaves
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1. What is simple harmonic motion?
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Motion when an object is disturbed and the
restoring force follows the formula F -kx.
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2. Which of these are examples of simple harmonic
motion?  A. a pendulum B. a weight on a
spring C. a plucked guitar string D. a
weightlifter doing five repetitions E. an
oboe player tapping her foot F. a bouncing ball
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2. Which of these are examples of simple harmonic
motion?  A. a pendulum B. a weight on a
spring C. a plucked guitar string D. a
weightlifter doing five repetitions E. an
oboe player tapping her foot F. a bouncing ball
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3a. A mass on a spring is oscillating. Describe
the net force, acceleration, and velocity of the
mass when it crosses the equilibrium position.
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The net force is and acceleration are zero. The
velocity is at its maximum.
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3b. Describe the net force, acceleration, and
velocity of the mass when it is at the point of
maximum displacement.
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The net force and the acceleration are at their
maximum. The velocity is at zero.
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4. What is the spring constant of a spring if a
force of 100 N stretches the spring 20 cm?
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F kx100 N k(.2 m)k 500 N/m
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5. A spring is compressed 10 cm. If the restoring
force is 200 N, what is the spring constant?
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F kx200 k(0.1 m)2000 N/m k
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6. A weight oscillating on a spring is held next
to a meter stick. If the center of mass of the
weight oscillates from the 10 cm point to the 40
cm point, what is the amplitude of the
oscillation?
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The distance of oscillation from maximum
displacement to maximum displacement is 30 cm.
The equilibrium position is halfway between.
Since amplitude is from equilibrium position to
maximum displacement, the amplitude is 15 cm.
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7. A pendulum swings through a total angle of
38. What is the angle of amplitude?
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Half the total, 19.
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8. How does period relate to frequency?
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T 1/f or f 1/T
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9. How does period relate to amplitude?
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Period and amplitude are NOT related to each
other.
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10. If the frequency of an oscillator is 20 Hz,
what is the period?
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T 1/fT 1/20T 0.05 s
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11. How should you change the length of a
pendulum to double the period?
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T 2pv(l/g)If I want the period T to double,
the v(l/g) must be 2 times as much, therefore the
length l must be increased to four times the
length, because the v4 is 2.
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12. What is the period of a 2 kg mass in simple
harmonic motion with an amplitude of 20 cm if
the spring constant is 400 N/m? What is the
frequency?
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T 2pv(m/k)T 2pv(2/400)T 0.44 sf 1/T
1/0.44f 2.25 Hz
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13. How would the period in problem 12 change if
the amplitude were 40 cm?
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None, amplitude doesnt affect period or
frequency.
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14. What is the period of a 2 m pendulum?
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T 2pv(l/g)T 2pv(2/10)T 2.8 s
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15. What would be the period of the same 2 m
pendulum on the moon where g is 1/6th as much?
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T 2pv(l/g)T 2pv2/(10/6)T 6.9 s
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16. Describe the motion of a single particle in a
transverse wave.
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In a transverse wave the particles move
perpendicular to the direction of the wave.
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17. Describe the motion of a single particle in a
longitudinal wave.
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In a longitudinal wave the particles move
parallel to the direction of the wave.
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18. Which type of wave are sound waves?
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Sound waves are longitudinal.
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19. What is the speed of a sound wave if the
frequency is 512 Hz and the wavelength is 0.7 m?
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v f lv 512 x 0.7v 358 m/s
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20. If a wave travels 14 m/s and a floating duck
bobs up and down once every 3 seconds, what is
the wavelength of the wave?
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3 seconds is the period, T 1/f, so the
frequency is 1/3 Hzv f l14 1/3 x ll 42 m
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21. What is the difference in constructive and
destructive interference?
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In constructive interference the amplitude is
increased in destructive interference the
amplitude is decreased.
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22. Which of these are examples of constructive
interference and which of these are examples of
destructive interference?  A. noise-canceling
headphones B. a dead spot in a movie
theater C. an earthquake causes a building to
fall D. a singer breaks a glass with his voice
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22. Which of these are examples of constructive
interference and which of these are examples of
destructive interference? D A. noise-canceling
headphonesD B. a dead spot in a movie
theaterC C. an earthquake causes a building to
fallC D. a singer breaks a glass with his voice
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23. What are fixed-end termination and free-end
termination?
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Fixed-end there is a change in phase at
reflection.Free-end there is no change in phase
at reflection.
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24. What is a standing wave?
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When two waves of the same amplitude and
frequency cross over each other and produce
pattern of loops and nodes.
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25. Draw a string vibrating at the 3rd harmonic.
How many nodes are present? How many antinodes
are present? How many loops are present?
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Three loops and antinodes (same thing), four
nodes.
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26. Draw a transverse wave. Label the crest,
trough, wavelength, and amplitude.
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Crests are the high points, troughs are the low
points.
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