Page 48 - Q & A STPM 2022 Physics

Physics Semester 3 STPM Chapter 21 Sound Waves

(b) Mass per unit length of string Q, m =  πd 2  ρ ∝ d 2
4
Mass per unit length of string R, m’ = (1.50) m
2
1
f Q = T Q = 440 Hz
2L m
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T Q
Fundamental frequency of string R, f R = 1 1.50 m
2
2(1.20)L
= 1 (440) Hz
(1.20)(1.50)
= 244 Hz

Section C Essay Question

Question 14
(a) A small loudspeaker which is connected to an audio oscillator of adjustable
frequency is held at the open end of a burette which is filled with water. The
water is then slowing run off from the burette. First resonance occurs when
the length of the air column in the burette is 7.2 cm, and again at 20.2 cm.
(i) What is the frequency of sound from the loudspeaker?
(ii) Determine the end correction.
(Speed of sound in air = 330 m s )
–1
(b) The frequency of the oscillation can be varied and read from a meter.
Describe how would you use the arrangement described in (a) above to
determine experimentally the speed of sound in air. You should state the
measurements to be taken, and how the speed of sound is deduced from
a suitable graph.

Answer
(a)
c c
7.2 cm

20.2 cm

Semester
3

408

021 STPM Q&A Physics T3.indd 408 17/02/2022 10:24 AM