**Your answer to Q45: **Sorry, your answer is **not **correct.
You should realize that the waves will interfere constructively. Where have
they each moved after 5 s?

Help: *Fundamentals of
Sound* reference: Secs. 1-C, 1-K.

Or, would you like a HINT?

You should really try to
work out the answer on your own, but if you insist on reading it, the correct
answer is here.

Return to Question
45.

**Hint
for Q45: **At a speed of 1/2 ft/s the two pulses each will have moved
2.5 ft in the 5 seconds. Think how they will add together when they are both
at the position corresponding to this.

Return to Question 45.

**Your
answer to Q45**: Congratulations, your answer is **correct**!

If you like, you can compare your answer to the "official" correct answer.

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45.

**Correct
answer to Q45**: Each pulse moves 2.5 feet in 5 seconds when moving
at 2.5 feet per second. This puts the center of each pulse at precisely the
same place, namely at *x* = 5.0 The rules of constructive interference
then mean that the pulses instantaneously add up to make a single total pulse.
Placing them "on top of each other" gives a square pulse that is the same width
as the original but twice as high. The answer is d).

Return to Question
45.

**Your answer to Q50**: Sorry, your answer is **not
**correct. Consult the definitions.

Help: *Fundamentals of
Sound* reference: Sec. 1-G.

Or, would you like a HINT?

You should really try to
work out the answer on your own, but if you insist on reading it, the correct
answer is here.

Return to Question
50.

**Hint
for Q50**: The only tricky parts of this are the difference beween "amplitude"
and "displacement." Look up "amplitude."

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50

**Your
answer to Q50: **Congratulations, your answer is **correct**!

If you like, you can compare your answer to the "official" correct answer.

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50

**Correct
answer to Q50**: (a)=(4); (b)= (5); (c)=(1); (d)=(2); (e)=(3);
(d)=(6).

Note the distinction between "amplitude" and "displacement." Amplitude is the
**maximum** distance a point moves from equilibrium (the rest position) to
a crest, while the displacement of a point on the wave measures just how far
that point, not necessarily a crest, is above equilibrium. Displacement is always
less than or equal to amplitude.

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**Your answer to Q55**: Sorry, your answer is **not **correct.
What have these items got in common with a wave?

Help: *Fundamentals of
Sound* reference: Sec. 1-E.

Would you like a HINT?

You should really try to work out the answer on your own, but if you insist on reading it, the correct answer is here.

Return to Question
55.

**Hint
for Q55: **Sec.1-F of *Fundamentals of Sound* points out that one
can make a plot of position versus time for certain oscillating objects. How
would you do this and what relation would that have to a wave?

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to Question 55

**Your
answer to Q55: **Congratulations, your answer is **correct**!

If you like, you can compare your answer to the "official" correct answer.

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55

**Correct
answer to Q55**: In both cases one can plot position away from equilibrium
as a function of time. The plot looks just like a sinusoidal waveform.
Indeed any one point of, say, a rope on which a sinusoidal traveling wave is
passing moves precisely like one of these oscillating objects. See the detailed
discussion in Sec. 1-F. The correct answer is c).

Return to Question
55

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