Second Examination
Physics 104
26 October 1982

#1.  At the bottom of a swimming pool is a drain pipe which has a 6.0 inch inner diameter.  the opening of the pipe is covered by a simple, water-tight cover lying on top of the opening.  If the depth of the water in the pool is  8.0 ft at the position of the pipe, and the pipe is filled with air and open to the atmosphere, then the force (in lb) needed to raise the cover up off the pipe is most nearly equal to


Answer:

a) 14,100     b) 31    c) 48     d) 499     e) 98    

#2.  A small boat is approximately 12 feet long and 3 feet wide, and it weighs 100 lb.  By filling it with water and then emptying it out, it is found that the maximum displacement of the boat is 43 cubic feet.  The amount of weight (in lb) that can be added to the boat so that it will just barely float is most nearly equal to
Answer:

a) 2246     b) 2146     c) 2583     d) 4300     e) 100

#3. Water flows at a speed of 5.0 m/s in a horizontal pipe.  The pipe tapers down to join with a smaller horizontal pipe with just half the cross-sectional area.  The difference in water pressure in going from the larger to the smaller pipe is most nearly equal to 
Answer:

a) zero      b) 3.75 ´ 104      c) 2.50 ´ 104      d) 5.00 ´ 104      e) 10.0 ´ 1034     

#4.   A siphon has a cross-sectional area of  0.750 cm2.  It is connected as shown in the sketch to a container of fluid with a specific gravity of 0.800 and negligible viscosity.  The fluid flows from the bottom end of the siphon at a rate (in  cm3/s) most nearly equal to

 


Answer:

a) 148      b) 119      c) 163      d) 182      e) 243

#5.  A transverse wave on a string that has a wavelength of  1.65 m and obeys the following wave equation:

2y / x2 =  ( 8.26 ´ 10-5)  2y / t2

 where x and y are in meters and t is in seconds.  The frequency (in Hz) of the wave is most nearly equal to 
Answer:

a) 66.7   b)2.00 ´ 103 c)1.36 ´ 10-3 d) 733.7 e) - 1.50 ´ 10-3

#6. A string vibrates according to the equation

y =          (0.75 cm)  ´   [sin (p x / 4 cm) ]  ´   [ cos (25p t /sec) ]

If the strength has a length 12 m, then it is vibrating with its 

Answer:

a) first harmonic  b) first overtone  c) fundamental  d) third harmonic   e) second harmonic
#7. A transverse sinusoidal wave is described by the equation

y = (3.0 m) ´  sin [ 2 p x /m - 11 p t /s - p/2]

The phase speed (in m/s) of the wave is most nearly equal to

Answer:

a) 22 b) 1.8 c)  5.5 d) 33p e)  6p
#8. For the wave in problem #7,  the maximum transverse speed (in cm/sec) of a point on  the wave is most nearly equal too 

  Answer:

a) 22    b) 1.8     c) 5.5    d) 33p  e) 6p
#9. An acoustic interferometer containing air is pictured in the sketch.  S is a sound source, and B is a detector.  Path SBD can be varied in length, but path SAD is fixed.  The sound intensity has a minimum that steadily increases to a maximum  as B is shifted by 2.16 cm to the right.  The wavelength (in cm) of the sound wave emitted by the source is most nearly equal to

Answer:
a) 0.54    b) 1.62    c) 4.32  d) 8.64  e) 17.28
#10. An open/closed organ pipe has a length of 1.20 m. Its fundamental frequency (in Hz) is most nearly equal to 

Answer:

a) -4.4    b) 68.8   c) +17.2   d) 275   e) 138
#11.  Two identical tuning forks have identical frequencies of 440 Hz.  One of the tuning forks is then placed next to an observer at rest, while the other tuning fork moves toward the observer at an unknown speed.  The speed of sound in air is 330 m/s.  With both forks sounding, an observer hears a beat frequency of 5.0 Hz.  The speed of the moving fork (in m/s) is most nearly equal to

Answer

a) 3.71    b) 3.75    c) 7.50   d) 88.0  e) 1.14

#12. A point sound source emits 1.0 watts of sound power isotropically.  At a distance of 2.0 m from the source, the sound level (in dB) is most nearly equal to
Answer:
a) 100    b) 2.0  c) 0.50    d) 0.040    e) 0.25
#13. A thermometer reads a temperature of 100 oK.  The same temperature in Degrees Rankin (oR) is most nearly equal to

Answer:

a) 100    b) 55.6    c) 212   d) 173.15   e) 180
#14. A uniform solid substance has a linear coefficient of expansion a. If its temperature is increased by DT, then the change Dr in its density, r, is
Answer
a) r/(3a DT)  b) - ar DT   c) -2r/(3a DT)  d) - 3ar DT   e) zero
#15. A glass (a = 1.0 ´ 10-5/oC ) tube 1.0 m long is half filled with a liquid (a = 1.0 ´ 10-5/oC ) at 20 oC.  When the tube and liquid are raised to a temperature of 35oC, the change (in mm) in the height of the liquid column is most nearly equal to

Answer:

a) 0.075    b) 0.30    c) 0.15    d) -0.30    e) zero