[ Questions #1-#13 |
Questions #14-#26 | Questions
[ #27 | #28 |
#29 | #30 | #31
| #32 | #33 |
#34 | #35 | #36
| #37 | #38
Diagram P at the right shows a transverse pulse traveling along a
dense rope toward its junction with a less dense rope. Which of
the diagrams (A, B, C, D, or E) below depicts the ropes at the
instant that the reflected pulse again passes through its original
position marked X? Consider such features as amplitude and
relative speed (i.e., the relative distance of the transmitted and
reflected pulses from boundary).
A, B, and C can be quickly ruled
out since it shows the amplitude of the reflected and
incident pulse to be the same size. An incident pulse
would give up some of its energy to the transmitted pulse
at the boundary, thus making the amplitude of the
reflected pulse less than that of the incident pulse.
Rule out D since it shows the reflected pulse moving
faster than the transmitted pulse. This would not happen
unless moving from less dense to more dense. This leaves
E as the answer.
28. A wave whose speed in
a snakey is 4.4 m/s enters a second snakey. The wavelength changes
from 2.0 m to 3.0 m. The wave in the second snakey travels at
a. 1.46 m/s.
b. 2.2 m/s.
c. 2.9 m/s.
d. 4.4 m/s.
e. 6.6 m/s.
This is another boundary
behavior question with a mathematical slant to it. The
frequency of the incident and transmitted waves are
always the same. Thus, use f =v/w to find the frequency
of the incident wave - 2.2 Hz. The frequency of the
transmitted wave is >also 2.2 Hz, the wavelength is
3.0 m, and so the speed is f*w = 6.6 m/s.
The diagram at the right shows a disturbance moving through a rope
towards the right. If this disturbance meets a similar disturbance
moving to the left, then which one of the diagrams below depict a
pattern which could NEVER appear in the rope?
WOW! Tough one. Draw a second
wave to the right of the wave which is given. Then
visually move the wave to the left. Visualize in your
mind the shape of the resultant as interference occurs.
It will never look like D. If you still don't get it,
take a break and watch some TV.
30. A 2.0-meter long rope
is hanging vertically from the ceiling and attached to a vibrator.
A single pulse is observed to travel to the end of the rope in
0.50 s. What frequency should be used by the vibrator to maintain
three whole waves in the rope?
a. 0.75 Hz
b. 1.33 Hz
c. 4.0 Hz
d. 6.0 Hz
e. 8.0 Hz
The given info allows you to
determine the speed of the wave: v=d/t=2 m/0.5 s) = 4
m/s. If there are 3 waves in a 2-meter long rope, then
each wave is 2/3-meter long. Now find frequency with the
equation v=f*w where v=4 m/s and w=0.667 m. Proper
algebra yields 6 Hz as the answer.
31. A Standing wave
experiment is performed to determine the speed of waves in a rope.
The standing wave pattern shown below is established in the rope.
The rope makes 90 complete vibrational cycles in one minute. The
speed of the waves is ____ m/s.
If there are 90 vibrations in 60
seconds, then there is a frequency of 1.5 Hz. The diagram
shows 1.5 waves in 6-meters of rope; thus, the wavelength
is 4 meters. Now use the equation v=f*w to calculate the
speed of the wave. Proper substitution yields 6.0
32. Consider the standing
wave pattern shown below. A wave generated at the left end of the
medium undergoes reflection at the fixed end on the right side of
the medium. The number of antinodes in the diagram is
An antinode is a point on the
medium which oscillates from a large + to a large -
displacement. Count the number of these points - there
are 6 - but do not count them twice.
33. A node is a point
located along the medium where there is always ___.
a. a double crest.
b. a double trough.
e. a double rarefaction.
A node is a point along the
medium of no displacement. The point is not displaced
because destructive interference occurs at this
34. TRUE or
Constructive interference of
waves occurs when two crests meet.
Yes! Or when a trough meets a
trough or whenever two waves displaced in the same
direction (such as both up or both down) meet.
35. Which phenomenon is
produced when two or more waves passing simultaneously through the
same medium meet up with one another?
Interference is the meeting of
two or more waves when passing along the same medium - a
basic definition which you should know and be able to
36. Two pulses are
traveling in opposite directions along the same medium as shown in
the diagram at the right. Which diagram below best depicts the
appearance of the medium when each pulse meets in the
When a crest is completely
overlapped with a trough having the same amplitude,
destructive interference occurs. Complete cancellation
takes place if they have the same shape and are
37. TRUE or
A vibrating object is necessary
for the production of sound.
Absolutely! If you don't believe
it, then think of some sounds - voice, guitar, piano,
tuning fork, chalkboard screech, etc. - and consider what
the vibrational source is. All sounds have a vibrating
object of some kind as their source.
38. Which one of the
following CANNOT transmit sound?
a. Liquid air
b. Gaseous oxygen
c. Liquid water
d. Solid steel
e. Perfect vacuum
Sound is a mechanical wave and
as such requires a medium in order to move through space.
For this reason, sound cannot move through a vacuum.
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