Graph 1 shows the speed of sound in air as a function of temperature. The data points were obtained by measuring the apparent height of the ceiling with MacMotion and a distance probe set for 20°C.
Velocity of Sound in Air versus Temperature
1 An extrapolation of the extent shown is....
a .... a normal procedure.
b.... justified since the speed of sound at zero degrees Celsius is known to be 331.5 m/s.
c.... a reliable prediction.
d.... never justified.
2 The speed of sound at a temperature of 40°C is likely to be....
a.... 356 m/s
b.... 355.80 m/s
c.... 331.5 m/s
d.... 340 m/s
3 The position probe (bat) emits short sound pulses at a frequency of 40 000 Hz. Sound of these frequencies is referred to as....
a.... Ultrasound
b.... Infrasound
c.... Radar
d.... Microwaves
4 The wavelength of the sound waves at 24°C is close to....
a.... 8.65 mm
b.... 1.0 mm
c.... 10.0 mm
d.... 364 mm
5 The distance resolution of the probe is close to ±0.1 mm. The resolution could be further improved by....
a.... lowering the pulse frequency.
b.... raising the pulse frequency.
c.... increasing the duration of the pulses.
d.... increasing the intensity of the pulses.
6 The computer calculates the distance to an object by using the time it takes for a pulse to reach the object and to be reflected back to the detector. If do is the true distance, vo is the velocity of sound at 20 degrees Celsius and d is the apparent distance to the object at some other temperature T . The speed of sound at T degrees Celsius is given by....
7 The speed of sound is higher in less dense (warmer) air. Would you expect the speed of sound in more humid air to be....
a.... slightly higher
b.... slightly lower
c.... unaltered
d.... impossible to predict - on the basis of the evidence.
8 The relationship v = 331.5 + 0.6T is likely to....
a.... be approximately correct for air over the room temperature range.
b.... apply to any gas over the room temperature range.
c.... be of little practical use for predicting the speed of sound in air.
d.... to be true only for dry air at zero degrees Celsius.
9 At a higher temperature a real bat will....
a.... slightly over estimate the size of a room.
b.... slightly under estimate the size of a room.
c.... believe the room to have expand slightly.
d ... believe the room to have contracted slightly..
*10 Real insect eating bats catch insects in flight. Would you expect a real bat to have temperature compensation 'software' built into its brain?
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