K.C.S.E Physics Q & A - MODEL 2008PP2QN15

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.
(ii) Given that t= 4/vx 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