PHY 102 - Chapter 9 Test Exam Questions and Correct Answers Latest Update 2024 ( Already Passed)
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PHY 102 - Chapter 9
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PHY 102 - Chapter 9
PHY 102 - Chapter 9 Test Exam Questions and Correct Answers Latest Update 2024 ( Already Passed)
A tuning peg slips on your violin, lessening the tension in one of the strings. What effect does this change have on the string's sound? - Answers It lowers the pitch (vibrational frequency) of the str...
PHY 102 - Chapter 9 Test Exam Questions and Correct Answers Latest Update 2024 ( Already Passed)
A tuning peg slips on your violin, lessening the tension in one of the strings. What effect does this
change have on the string's sound? - Answers It lowers the pitch (vibrational frequency) of the string.
(The string's pitch (vibrational frequency) depends on its inertia and on the stiffness of its restoring
force. Decreasing the string's tension softens the restoring force so that the string accelerates more
slowly and takes longer to complete each cycle of its motion.)
Why are the highest pitched strings on most instruments, including guitars, violins, and pianos, the most
likely strings to break? - Answers To vibrate at the highest pitches, these strings must be thin and taut.
That combination makes them prone to breaking.
(Because they must vibrate rapidly, the highest pitch strings are typically thin, taut, and short. While the
string's length has no significant effect on its tendency to break, its thinness and tension definitely do.
The high-pitched strings are typically so thin and so taut that they are always in danger of breaking.)
Why would replacing the air inside a metal organ pipe with helium gas raise the pipe's pitch? - Answers
Helium is less dense than air, so it accelerates more rapidly than air.
(When the air column inside the pipe vibrates, its pitch (frequency) is determined by the air column's
mass and stiffness. Replacing the air with helium doesn't affect the stiffness of that column because
squeezing the helium column inward a given amount is just as difficult as squeezing the air column
inward a given amount. But the helium column has far less mass than the air column, so it completes
each cycle of oscillation in far less time than the air column.)
Why are the tides relatively weak near the north and south poles? - Answers The moon's gravity
produces two tidal bulges in the earth's oceans. Those tidal bulges peak near the equator, one on the
side of the earth nearest the moon and one on the side of the earth farthest from the moon.
(On the side of the earth nearest the moon, the moon's gravity is stronger than its average value for the
earth. As a result, the water there bulges up toward the moon. On the side of the earth farthest from
the moon, the moon's gravity is weaker than its average value for the earth. The water there bulges up
away from the moon. But around the middle of the earth, a ring that includes the north and south poles,
the moon's gravity is at its average value for the earth and the water doesn't bulge. Moreover, as the
earth rotates, the strength of the moon's gravity at the poles doesn't change and neither does the
height of the water there.)
, If you pull downward on the middle of a trampoline and let go, the surface will fluctuate up and down
several times. Why is this motion an example of a standing wave? - Answers The trampoline's nodes and
antinodes do not move.
(A standing wave is one in which the nodes and antinodes remain in place, even as the crests and
troughs oscillate back and forth about equilibrium.),
Even when waves don't break as they pass over a sandbar, the sandbar is noticeable because you can
see the wave crests move closer together. What is happening to cause this bunching? - Answers The
wave's speed decreases as it passes through shallow water and since its frequency doesn't change, its
wavelength decreases.
(The wave slows in shallow water, but its frequency can't change. Since the wave's speed is the product
of its wavelength times its frequency, a decrease in its speed must be accompanied by a decrease in its
wavelength. In this case, the wave's crests bunch up in the shallow water.)
Sound can pass from one paper cup to another through a long, taut string that connects their bottoms.
What type of wave is present in the string when your voice shakes the bottom of your cup in and out
and your friend hears your voice from the other cup. - Answers The string has a longitudinal traveling
wave.
(As the wave passes along the string, each portion of that string vibrates parallel to the string itself, so
the wave is longitudinal. The wave's crests and troughs travel along the wave, so it is a traveling wave.)
You whistle twice, sending out two sound waves. Can you make the second sound wave overtake the
first and, if so, how? - Answers No.
(Sound waves in air do not exhibit dispersion: they all travel at the same speed regardless of pitch.
Moreover, the volume of a sound wave has no effect on its speed.)
If you stand in front of a stone building and clap your hands, you hear an echo. What is happening to the
sound wave to cause this echo? - Answers The sound wave is being reflected by the stone surface.
(When a sound wave traveling through air tries to enter stone, that wave is almost perfectly reflected.
Sound waves in air and sound waves in stone travel at different speeds and with different mechanical
characteristics, so sound has great difficulty crossing the interface between the two materials.)
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