K.C.S.E Physics Q & A - MODEL 2019PP2QN05
​In a siren, sound is produced when a jet of air is directed perpendicular to a ring of holes on a rotating wheel. Explain the effect on the pitch of sound produced when the speed of rotation of the wheel is increased.
answer
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K.C.S.E Physics Q & A - MODEL 2018PP2QN01
Explain why the walls of a studio are padded with woollen materials
answer
K.C.S.E Physics Q & A - MODEL 2017PP2QN03
State one use of echoes.
answer
K.C.S.E Physics Q & A - MODEL 2016PP2QN18
​(a)State one factor that affects the speed of sound in a solid.
b)An observer stands half-way between two vertical cliffs that are L metres apart.He strikes a gong and measures the time interval, t, between the echoes heard from the two cliffs. He moves a further 10m and again strikes the gong and measures the time interval between the echoes. The process is repeated several times. The graph in Figure 13 shows the relation between the time interval, t and the distance, x from the centre. (i)From the graph, determine the value of x for which the time interval was 0.55. 
​(ii)Given that t = 4x/v where v is the speed of sound in air, determine the value of v from the graph.
(iii)If the maximum time measured by the observer was t=4.7s, determine the distance L between the cliffs. (c)A search boat uses a signal of frequency 6.0 x 104 Hz to detect a sunken ship directly below. Two reflected signals are received; one after 0.1 seconds from sunken boat and the other after 0.14 seconds from the sea bed. If the sea bed is 98 m below the boat, determine:- (i)The speed of the signal in water. You may use the value of v from (ii) above. (ii)The depth of the sunken ship below the boat
answers
​(a)Temperature
Density (b)(i)47 metres (ii) 
​(iii)Distance = speed x time
2D = distance to and from the cliff 2D = 340.715 x 4.7 D = 800.68 metres (c)(i)Distance moved by sound from sea bed = 98 x 2 m V = (98 x 2)0.14 = 1400 m/s (ii) Distance = v x t = 1400 x 0.10/2 = 70 m K.C.S.E Physics Q & A - MODEL 2016PP2QN14
​Figure 6 shows a simple electric bell circuit
​(i)Name the parts labeled
(I) D (II) E (ii)When the switch is closed, the hammer hits the gong repeatedly. Explain why: (I) the hammer hits the gong. (II) the hammer hits the gong repeatedly. (b) An electric bulb is rated 60 W, 240 V. Determine: (i) the current that flows through it when it is connected to a 240 V supply. (ii) the resistance of the bulb.
answers
​(i)D-Soft iron armature
E-Contact screw (ii) (I)Soft iron core is magnetized It attracts the armature (II) Contact is broken The core then loses magnetism Armature spring back making contact again 
K.C.S.E Physics Q & A - MODEL 2016PP2QN13
​A boy standing in front of a cliff blows a whistle and hears the echo after 0.5s. He then moves 17 metres further away from the cliff and blows
the whistle again. He now hears the echo after 0.6s. Determine the speed of the sound.
answer
K.C.S.E Physics Q & A - MODEL 2015PP2QN09
​A ship in an ocean sends out an ultra sound whose echo is received after 3 seconds. If the wavelength of the ultra sound in water is 7.5 cm, and the frequency of the transmitter is 20 kHz, determine the depth of the ocean.
answer
K.C.S.E Physics Q & A - MODEL 2014PP2QN017
(a) Figure 9 shows two speakers and S2 which produce sound of the same frequency.
They are placed equidistant from a line AB and a line PQ. (PQ is perpendicular to line AB). 
​(i) A student walking from A to B hears alternating loud and soft sounds. Explain why at some point the sound heard is soft.
(ii) The student now walks along line PQ. State with reason the nature of the sound the student hears. (b) Figure 10 shows sound waves in air produced by a vibrating tuning fork. R is an air molecule on the path of the waves. 
​(i) Using a line, indicate on the diagram a distance d equal to one wavelength of the wave.
(ii) In the space provided, show with an arrow the direction of motion of the air molecule R as the waves pass. (iii) Explain the reason for the answer in (ii).
answers
​(a) (i) (I) sound is soft when the waves arrive out of phase;such waves undergo destructive interference.
(ii) same sound — loud. Along PQ the waves undergo constructive interference as they arrive in phase. 
​(iii) As the longitudinal waves pass molecule R moves along to either side.
For a crest. R moves away from source. K.C.S.E Physics Q & A - MODEL 2009PP2QN12
​ A boy standing in front of a cliff blows a whistle and hears the echo after 0.5s. He then moves 17 metres further away from the cliff and blows the whistle again. He now hears the echo after 0.6s. Determine the speed of the sound.
answer
K.C.S.E Physics Q & A - MODEL 2008PP2QN15
​ a) State one factor that affects the speed of sound in a solid.
b) An observer stands half-way between two vertical cliffs that are L metres apart. He moves directly towards one cliff and after a distance x=10cm from the centre, he strikes a gong and measures the time interval, t, between the echoes heard from the two cliffs. He moves a further 10m and again strikes the gong and measure the time interval between the echoes. The process is repeated several times. The graph in Figure 8 shows the relation between the time interval, t and the distance, x from the centre. 
(i) From the graph, determine the value of x for which the time interval was 0.55.
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