# Physics 202 Midterm #2

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question
What has a greater density, 3 g of mercury or 500 g of water?
3 g of mercury
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Is the pressure the water at point A (under a ship) greater than, smaller than, or equal to the pressure of point B (open water)
Two points on a horizontal line, connected by a single liquid in hydrostatic equilibrium, are at the same pressure. pA=pB
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The pressure at 10 m below the surface of the ocean is about 2.00×105 Pa . Which statement is true?
The weight of a column of seawater 1 m2 in cross section and 10 m high plus the weight of a column of air with the same cross section extending up to the top of the atmosphere is about 2.00×105 N.
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The pressure at 10 m below the surface of the ocean is about 2.00×105 Pa . Now consider the pressure 20 m below the surface of the ocean. Which of the following statements is true?
The pressure is equal to that at a depth of 10 m plus the weight per 1 m2 cross sectional area of a column of seawater 10 m high.
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The magnitude of the buoyant force is equal to the weight of fluid displaced by the object. Under what circumstances is this statement true?
for every object submerged partially or completely in a fluid
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The magnitude of the buoyant force is equal to the weight of the amount of fluid that has the same total volume as the object. Under what circumstances is this statement true?
for an object completely submerged in a fluid
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The magnitude of the buoyant force equals the weight of the object. Under what circumstances is this statement true?
for an object that floats
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The magnitude of the buoyant force is less than the weight of the object. Under what circumstances is this statement true?
for an object that sinks
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An object is floating in equilibrium on the surface of a liquid. The object is then removed and placed in another container, filled with a denser liquid. What would you observe?
The object would float submerged less deeply than in the first container.
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An object is floating in equilibrium on the surface of a liquid. The object is then removed and placed in another container, filled with a less dense liquid. What would you observe?
More than one of these outcomes is possible.
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Two objects, T and B, have identical size and shape and have uniform density. They are carefully placed in a container filled with a liquid. Both objects float in equilibrium. Less of object T is submerged than of object B, which floats, fully submerged, closer to the bottom of the container. Which of the following statements is true?
Object B has a greater density than object T.
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The spring can be either stretched or compressed. The block slides on a frictionless horizontal surface, as shown. When the spring is relaxed, the block is located at x=0. If the block is pulled to the right a distance A and then released, A will be the amplitude of the resulting oscillations. After the block is released from x=A, it will
move to the left until it reaches x=−A and then begin to move to the right
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If the period is doubled, the frequency is
halved
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An oscillating object takes 0.10 s to complete one cycle; that is, its period is 0.10 s. What is its frequency f?
10 Hz
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If the frequency is 40 Hz, what is the period T ?
0.025 seconds
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Which points on the x axis are located a distance A from the equilibrium position?
both R and Q (min and max amplitudes)
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Suppose that the period is T. Which of the following points on the t axis are separated by the time interval T?
K and P (where slope crosses 0 with a slope to the right)
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Now assume for the remaining Parts G - J, that the x coordinate of point R is 0.12 m and the t coordinate of point K is 0.0050 s. What is the period T ?
0.02 seconds
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Now assume for the remaining Parts G - J, that the x coordinate of point R is 0.12 m and the t coordinate of point K is 0.0050 s. How much time t does the block take to travel from the point of maximum displacement to the opposite point of maximum displacement?
0.01 seconds
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Now assume for the remaining Parts G - J, that the x coordinate of point R is 0.12 m and the t coordinate of point K is 0.0050 s. What distance d does the object cover during one period of oscillation?
0.48 meters
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Now assume for the remaining Parts G - J, that the x coordinate of point R is 0.12 m and the t coordinate of point K is 0.0050 s. What distance d does the object cover between the moments labeled K and N on the graph?
0.36 meters
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If the bob's mass is doubled, approximately what will the pendulum's new period be?
T
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If the pendulum is brought on the moon where the gravitational acceleration is about g/6, approximately what will its period now be?
T√6
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If the pendulum is taken into the orbiting space station what will happen to the bob?
It will no longer oscillate because both the pendulum and the point to which it is attached are in free fall.
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If you need to raise the frequency of a particular glass, should you add water or remove water?
remove water
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If you drive an oscillator, it will have the largest amplitude if you drive it at its _______ frequency.
resonant
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A 100 Hz sound wave is traveling through the air. If we increase the frequency to 200 Hz, this will _____ the wavelength.
decrease
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If the strings have different thicknesses, which of the following parameters, if any, will be different in the two strings?
wave speed and wavelength,
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If the strings have the same thickness but different lengths, which of the following parameters, if any, will be different in the two strings?
nothing will be different
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Sound waves in air are ______ waves
longitudinal
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A compression in a sound wave is a region where
pressure and density are higher than average and the air molecules are closer together than average
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As a sound wave spreads out from a point source its intensity decreases because
the surface area over which it acts increases
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How many times more intense is a 100 dB sound compared to a 50 dB sound?
100,000 times
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A source producing sound at a frequency of 1000 Hz moves towards Nancy and away from Pablo. Nancy hears the sound at a frequency
greater than 1000 Hz
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A source producing sound at a frequency of 1000 Hz moves towards Nancy and away from Pablo. Pablo hears the sound at a frequency
less than 1000 Hz
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A shock wave is produced
when the source of a wave travels faster than the speed of the wave
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When two waves overlap, the displacement of the medium is the sum of the displacements of the two individual waves. This is the principle of __________.
superposition
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The interference of two sound waves of similar amplitude but slightly different frequencies produces a loud-soft-loud oscillation we call __________.
beats
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A point on a standing wave that is always stationary is a(n) _____.
node
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You can decrease the frequency of a standing wave on a string by __________.
using a thicker string, decreasing the tension, and making the string longer
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We describe sound waves in terms of pressure. Given this, for a standing wave in a tube open at each end, the open ends of the tube are __________.
nodes
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Based on the information presented in the introduction of this problem, what is a sound wave?
Propagation of pressure fluctuations in a medium
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aving established that a sound wave corresponds to pressure fluctuations in the medium, what can you conclude about the direction in which such pressure fluctuations travel?
Pressure fluctuations travel along the direction of propagation of the sound wave.
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Does air play a role in the propagation of the human voice from one end of a lecture hall to the other?
yes
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Taking the speed of sound in air to be 344 m/s, what are the frequency f and the wavelength λ of the sound wave shown in the graph?
1000 Hz, 0.344 m
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A certain sound is recorded by a microphone. The same microphone then detects a second sound, which is identical to the first one except that the amplitude of the pressure fluctuations is larger. In addition to the larger amplitude, what distinguishes the second sound from the first one
It is perceived as louder
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A certain sound is recorded by a microphone. The same microphone then detects a second sound, which is identical to the first one except that it has twice the frequency. In addition to the higher frequency, what distinguishes the second sound from the first one?
It is perceived as higher in pitch.
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What varies between two tones that are different in timbre, that is, two tones that have the same fundamental frequency but are produced, say, by different musical instruments?
the harmonic content
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A Styrofoam brick and a lead brick have the same weight. Which of the following statements is/are correct? a) the two bricks have the same mass b) the volume of the styrofoam brick is greater than the volume of the lead brick c) the density of the lead rich is greater than the density of the styrofoam brick d) both a and b e) all of the above
e) all of the above
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An empty pop can had a small amount of water in it. The water was brought to boiling, the can was inverted, and its top was placed in cold water. What happened to the can?
the can was crushed
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A house window with an area of one square meter has a force on the outside of about 100,000 N due to atmospheric pressure. Why doesn't the window break from this force?
The pressure of the air inside the house produces an equal and opposite force that cancels out the force of the air outside of the house
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A heavy lead block and a light aluminum block of equal sizes are both submerged in water. Upon which is the buoyant force greater?
it is the same on both blocks (since they both displace the same amount of water)
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Why don't ships made of iron sink?
since the ship is not solid iron, the average density is less than the density of water
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Salt water is more dense than fresh water. Why does a boat float higher in salt water than in fresh water?
The volume of water that is displaced by the boat is less for salt water than for fresh water
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A mass is attached to an ideal spring and sliding on a frictionless surface is an example of a simple harmonic oscillator. Is the acceleration ever zero? If so, where?
Yes, when the mass passes through its equilibrium point (ex. when x=0)
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Several masses are hung from different springs and set vibrating. Which combination vibrated the fastest?
Small mass and stiff spring
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For the vertical mass-spring system, what can you say about its energy when the mass is at its lowest point? a) the system has its minimum amount of gravitational potential energy b) the system has its maximum amount of elastic and potential energy c) the system has zero kinetic energy (in the reference frame of the spring's support) d) both A and B e) all of the above
e) all of the above
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Where is the equilibrium position of a pendulum?
Directly in the middle (below the source)
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A mass was firmly attached to a spring. The other end of the spring was shaken at different frequencies. What did you observe about the amplitude of vibration of the mass?
The amplitude was small for low frequency and for high frequency; in between there was a frequency where the amplitude was very large
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A tank of water is on a vibrating platform. The water will slosh with large amplitude when the frequency of the platform ______
is about the same as the natural frequency of vibration of the water
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Two pulses travel to the right along the same thing, one after the other. Which one travels faster, or do they travel the same speed?
they travel the same speed (same medium = same speed)
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the relationship v= f(wavelength) means that the speed of a wave
equals the frequency times its wavelength. (speed depends on the properties of the medium)
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Why can no one hear you scream in space?
Sounds are not transmitted through space
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The difference in sound level in Autzen stadium when there are 50,000 screaming fans compared to when there are 25,000 screaming fans is about
3 dB
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The siren of a police car has a frequency of 1250 Hz when at rest. The police car is traveling to the right at 25 m/s, chasing a bank robber whose car is also traveling to the right at 20 m/s. The bank robber hears the siren at a frequency a)less than 1250 Hz b) equal to 1250 Hz c) greater than 1250 Hz d) the robber cannot hear the siren since the car is going slower than the police car
c) greater than 1250 Hz (relative motion is together)
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The siren of a police car has a frequency of 1250 Hz when at rest. The police car is traveling to the right at 25 m/s, chasing a bank robber whose car is also traveling to the right at 30 m/s. The bank robber hears the siren at a frequency a)less than 1250 Hz b) equal to 1250 Hz c) greater than 1250 Hz d) the robber cannot hear the siren since the car is going faster than the police car
a) less than 1250 Hz (since the relative motion is apart)
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The siren of a police car has a frequency of 1250 Hz when at rest. The police car is traveling to the right at 25 m/s, chasing a bank robber whose car is also traveling to the right at 25 m/s. The bank robber hears the siren at a frequency a)less than 1250 Hz b) equal to 1250 Hz c) greater than 1250 Hz d) the robber cannot hear the siren since the car is going faster than the police car
b) equal to 1250 Hz (since there is no relative motion)
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What happened when (a) two pool balls made a head-on collision, and (b) two wave pulses made a head-on collision? A. Both the pool balls and the wave pulses bounced off of each other. B. The pool balls bounced off each other; the wave pulses passed through each other. C. The pool balls passed through each other; the wave pulses bounced off each other. D.Both the pool balls and the wave pulses passed through each other.
B. The pool balls bounced off each other; the wave pulses passed through each other.
question
Two point sources produce identical sound waves. Where do the waves interfere