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26 Cards in this Set
- Front
- Back
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T/F. A wave only transfers energy from one point to another.
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False. A wave transfers both energy and momentum. It has kinetic energy, therefore, it must also have momentum.
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What is the formula to calculate the speed of a wave?
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v=f*wavelength
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T/F. When a sound wave moves through the air, the net movement of air molecules in the direction perpendicular to the propagation of the wave.
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False. Sound waves are longitudinal. By definition, the medium of a longitudinal waves moves back and forth parallel to the propagation of the wave, but the final displacement is zero. The wave described in the question is the definition of a transverse wave.
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What is the unit of frequency?
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Hz or # of cycles/sec
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T/F. A wave moves faster through a medium that resists change.
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True. This is why sound moves faster through a solid than the air. It returns to its original position more quickly than a gas because the molecules are more rigid.
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T/F. Wave velocity depends on the wave frequency and wavelength, and is independent of the medium.
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False. Wave velocity only depends on the medium.
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What would happen to the frequency of a wave, if the amplitude of the wave were doubled?
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It would remain the same. The only exception would be waves that are not tested on the MCAT.
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Change to which of the following would increase the intensity of a harmonic wave?
a. increase in velocity b. increase in frequency c. increase in amplitude d. increase in period |
velocity, frequency, and amplitude
-Intensity is directly proportional to the square of frequency. Therefore, it is inversely proportional to the period. Increasing the period, would decrease intensity because it would decrease frequency. |
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What are the SI units for intensity?
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W/m^2;
intensity=rate of energy transfer/surface area I=P/A |
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Which of the following is the greatest contributing factor to why sounds waves move faster through water than air?
a. water has greater density than air b. Water is less compressible than air c. Sound waves are longer in air d. Sounds waves have more energy in water |
Water is less compressible than air, thus their bulk modulus (Beta) (or resistance to change) is MUCH greater.
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T/F. The period of a sound wave is not related to the pressure changes.
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False. In a sound wave, molecules start at rest, then continuously move together and apart. When they are together, this is high pressure. Therefore, each period of a sound wave is the time between each pressure increase.
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If the frequency of a sound wave is double, what will happen to the speed?
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The speed will move at the same speed, since velocity of a wave is independent of frequency.
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If two pulses are equidistant from the listener, and each generates a single sound pulse, one of greater intensity than the other, which sound was generated first?
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This question is asking about velocity of sound (how quickly was the sound wave moving in relation to time). Therefore, it can be concluded that both were generated at the same time, since velocity of a wave is independent of intensity.
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What will increase intensity the most?
a. increase in wavelength b. amplitude c. density of the medium d. velocity of the wave |
density of the medium;
I= 1/2 (density)(angular freq^2)(amplitude^2)(velocity) |
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T/F. Two waves that move toward each other on a string will reflect and refract.
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False. The will neither refract nor reflect. These both involve a change in medium.
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T/F. Two waves move toward each other along the same string. When they meet, they will experience constructive interference but not destructive interference.
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False. They will experience both.
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T/F. The beat frequency describes a change in pitch.
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False. The beat frequency describes a change in intensity which occurs at a frequency equal to the difference between two sound sources.
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What is the relationship between intensity and the following three variables?
a. amplitude b. frequency c. velocity d. radius |
Intensity is directly proportional to A^2, f^2 and v and inversely proportional to r^2
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What is the relationship between intensity and decibels?
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10^x (change in Intensity) = x*10 (change in decibel). They change in direct proportion - either increase or decrease together.
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If a higher note is played, which of the following properties of sound wave must increase?
a. period b. wavelength c. amplitude d. frequency |
d. higher frequency correlates with higher pitch; velocity is dictated by medium, amplitude unchanged, period and wavelength must decrease with higher frequency: f=1/T, v=f*wavelength
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Which of the following is NOT simple harmonic motion?
a. an electron moving back and forth in an ac current b. the orbit of the earth around the sun as viewed from the side c. a pendulum swinging at a small angle d. a boy bouncing a yoyo in a steady stream |
d. a boy bouncing a yo-yo is harmonic motion, which is any cyclic motion. However, simple harmonic motion is any motion that can be described using a sine wave.
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Which of the following cannot be used described with a single sine wave function?
a. a mass bouncing up and down hanging from a spring b. any simple harmonic motion c. a guitar string vibrating at all harmonics d. a fishing bobber bouncing up and down on a series of uniform water waves |
c. a guitar string vibrating at all its harmonics is the sum of many sine waves. Each harmonic is a sine wave with a different frequency.
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T/F. A longer rope with the same tension would result in longer harmonics and higher resonance frequencies.
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False. A longer rope with constant tension would result in longer harmonics (L) and lower resonance frequencies (f) according to their relationship in L=nv/4f
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What is true about the oscillating energy concerning a system in simple harmonic motion?
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energy oscillates between potential and kinetic, but total energy remains constant.
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What is true about restoring force and displacement concerning a system in SHM?
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restoring force is directly proportional to the displacement (i.e., F=-kx)
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In SHM, what relationship will all periods (T) have to some inertial component (like m), and some elastic component (like k)?
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i.e., T=2(pi) sqrt (m/k)
T proportional to sqrt inertial (m) T inversely prop. to sqrt elastic (k) |
