Your answer to Q60: Sorry, your answer is not correct. Be sure you do not confuse medium motion with wave motion.
Help: Fundamentals of
Sound, Secs. 1-D, 1-G.
Or would you like a HINT ?
You should try to work out the answer on your own, but if you insist on reading it the correct answer is here
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60
Hint for Question 60: The medium motion and the wave motion are the ideas in question here. What is point B doing while the wave goes by?
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60
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Correct
answer to Q60: While a wave moves to the right, point B is moving up to
the maximum displacement, then back down to zero, and then to a negative displacement,
and finally back to equilibrium. That is a complete cycle, carried out in one
period, and describes the medium motion. b) is the correct answer.
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Your answer to question 65: Sorry, your answer is not correct. You should look up the definition of wavelength.
Help: Fundamentals of Sound, Secs. 1-D, 1-G.
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You should try to work out
the answer on your own, but if you insist on reading it the correct
answer is here
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65
Hint for question 65: Wavelength
is the distance between two adjacent crests of a wave, as, for example, the
peak to peak distance.
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Your answer to question 65: Congratulations, your answer is correct!
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65
Correct
answer to Question 65: The distance from one peak to the next is 2 feet.
You can also take the distance from any one point to the next precisely similar
point, for example, from a zero where the wave is going up, to the next zero
where it is again going up and has completed one cycle in space.
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Your answer to Question 70: Sorry, your answer is not correct. You should look up the definition of amplitude.
Help: Fundamentals of Sound, Secs. 1-D, 1-G.
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You should try to work it out on your own, but if you insist on reading it the correct answer is here.
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70
Hint for question 70: Amplitude
is the distance from the zero position (equilibrium or at-rest position) of
any point to the point where is at a maximum distance away from equilirium.
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70
Your answer to question 70: Congratulations, your answer is correct!
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Correct answer to question 70: The
amplitude is 1 foot. This is the distance from the at-rest position to the position
of a peak of a wave. The correct answer is a).
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70
Your answer to question 75: Sorry, your answer is not correct. You should look up the definition of period.
Help: Fundamentals of Sound, Secs. 1-D, 1-G.
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You should try to work out
the answer on your own, but if you insist on reading it the correct
answer is here.
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;
Hint for question 75: The
period is the time for one complete cycle.
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75
Correct answer to question 75: The period is the time for one complete cycle. Follow the point B as is moves up and then back down. It reaches its lowest point after 1.5 s, but that is not yet one complete cycle; it must next return back to its starting position, which it does by 2 seconds. The period is thus 2 seconds and the correct answer is d).
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75
Your answer to question 78: Sorry, your answer is not correct. You should look up the definition of frequency.
Help: Fundamentals of Sound, Secs. 1-D, 1-G.
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You should try to work out
the answer on your own, but if you insist on reading it, the correct
answer is here.
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Hint for question 78: The
frequency is the number of cycles occurring in one second (Hertz). Examine how
many cycles (or fractions of a cycle) point B has undergone after one second.
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78
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Correct answer to question 78: After one
second, point B has undergone only half a cycle, so that the the frequency is
0.5 Hertz. One can also use f=1/T = 1/(2 s) = 0.5 Hz.
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78
Your answer to question 80: Sorry, your answer is not correct. You should look up the definition of wave velocity.
Help: Fundamentals of Sound, Secs. 1-D, 1-G.
Or, would you like a HINT?
You should try to work out the answer on your own, but if you insist on reading it, the correct answer is here.
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80.
Hint for question 80: Wave
velocity is the distance traveled divided by the time to travel that distance.
Pick a point and see how far it travels in, say, 1 second.
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80.
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80.
Correct
answer to question 80: The wave travels one wavelength in one period. Thus
the wave velocity (distance over time) is 2 ft/2 s = 1 ft/s. Another way to
do this is to use the formula velocity = frequency x wavelength = 0.5 Hz x 2
ft = 1 ft/s.
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