Page 53 - SP015 Past Years PSPM Chapter 6 -14 Ver 2020

PSPM SP015

PSPM 2007/2008 SF017/2 No. 13(a)

51. A siren of an ambulance emits a sound of frequency 800 Hz. The ambulance moves at
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25 m s away from a stationary observer and towards the wall of a building. Calculate
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the beat frequency heard by the observer. Speed of sound is 330 m s . [5 m]

PSPM 2011/2012 SF016/2 No. 7(b)(ii)

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52. What frequency will be heard by a moving observer travelling at 25 m s towards a
stationary siren that emits a sound of frequency 280 Hz?
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(Velocity of sound in air = 343 m s ) [2 m]

PSPM 2015/2016 SF016/2 No. 7(b)

53. A man stands by the roadside when an ambulance passes by him with constant velocity
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18 m s . The ambulance emits siren with frequency 256 Hz. The speed of sound is
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340 m s .

(a) Calculate the apparent frequency of the siren heard by the man before the
ambulance passes him. [2 m]

(b) Sketch a graph of the apparent frequency against distance travelled. [1 m]

(c) Sketch a graph of siren intensity against distance. [1 m]

PSPM 2016/2017 SF016/2 No. 7(b)(ii)

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54. A car is travelling at 25 m s emits a sound of frequency 1100 Hz approaches a
stationary observer. Calculate the apparent frequency of the sound heard by the
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observer. The speed of sound is 340 m s . [2 m]

PSPM 2017/2018 SF016/2 No. 7(c)

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55. A submarine that travels in the water at a speed of 8 m s and emits a sonar wave of
frequency 1400 Hz is approaching another stationary submarine. Given the speed of
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sound in water is 1530 m s , calculate the apparent frequency as detected by an
observer in the stationary submarine. [2 m]

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