**Your
Answer to Q620.**
Sorry, your answer is **not** correct.

Help: *Fundamentals of
Sound*, Sec. 12-B.

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.

Return to Question 620.

**Hint
for Question 620:** The small force applied to the long arm can lift
the large force on the short arm.

Return to Question 620.

**Your
Answer to Q620. **Congratulations, your answer is **correct**.

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

Return to Question 620.

**Correct
Answer to Question 620:** The lengths of the arms are proportional the the
weights. The heavy weight is 10 times the small force and so the long arm (at
1 m) must be 10 times the length of the short arm, which is then 1/10 m. b)
is correct.

Return to Question 620.

**Your
Answer to Q625.** Sorry, your answer is **not** correct.

Help: *Fundamentals of
Sound*, Sec. 12-B.

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.

Return to Question 625 .

**Hint
for Question 625:** The amplification factor tells one by how much she can
enhance the force or pressure applied.

Return to Question 625 .

**Your
Answer to Q625. **Congratulations, your answer is **correct**.

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

Return to Question 625 .

**Correct
Answer to Question 625:** The 5 N force has been amplified by the lever into
a 50 N force. The amplification factor is 10. b) is the correct answer.

Return to Question 625.

**Correct
Answer to Question 630:** A megaphone is a cone shaped device whose
opening at one end is approximately the size of the open mouth. It gradually
widens to a much larger diameter, sometimes more than a foot across. In speaking,
sound is reflected at the lips because of the discontinuity between the air
tube of the vocal tract and the outside world. By having a cone that gradually
opens to the outside air, the impedance difference between the vocal tract and
the open air occurs gradually over the whole length of the megaphone rather
than suddenly at the lips. Because there is no sudden impedance difference anywhere,
less reflection occurs and more of the sound gets out of the vocal tract into
open air. A louder sound results to the hearer.

The megaphone also concentrates the sound somewhat by directing it over a somewhat reduced area, but that is likely a smaller effect.

Return to Question 630.

**Your
Answer to Q635.** Sorry, your answer is **not** correct.

Help: *Fundamentals of
Sound*, Sec. 12-K.

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 it is here.

Return to Question 635.

**Hint
for Question 635:** Pressure is force divided by area. What area is relevant
here?

Return to Question 635.

**Your
Answer to Q600. **Congratulations, your answer is **correct**.

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

Return to Question 635.

**Correct
Answer to Question 635:** Pressure is force divided by area. If there
are *M* nails, each nail provides a force of (700/*M*) Newtons to
support the body, on an area of 2x10^{-7} m^{2}. The pressure,
when there is a minimal number of nails, is then 5x10^{6} N/m^{2}
= 700/(*M*x2x10^{-7}) N/m^{2} .
Solve for *M* to get *M* = 700/(2x10^{-7}x5x10^{6})
= 700. e) is the answer.

Return to Question 635.

**Your Answer to Q640.** Sorry, your answer is
**not** correct.

Help: *Fundamentals of
Sound*, Sec. 11-K.

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.

Return to Question 640.

**Hint
for Question 640:** Does the basilar membrane work this way?

Return to Question 640.

**Your
Answer to Q640. **Congratulations, your answer is **correct**.

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

Return to Question 640.

**Correct
Answer to Question 640:** b) is correct. The description given fits
the volley theory (which is sometimes called the "telephone theory")
of hearing. For most frequencies our hearing is described by a place theory,
so that a particular position on the basilar membrane is associated with a particular
frequency. The diaphram in the old phone speaker has no particular position
associated with any frequency; the whole thing vibrates at each frequency. Waves
travel along the basilar membrane to the resonant position, so the traveling
wave theory is equivalent to a place theory. At very low frequencies the whole
basilar membrane is vibrating as a unit; at these frequencies there may be an
analogy with the telephone diaphram.

Return to Question 640.

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