Question

a sound wave has frequency 2Hz and wavelength 40 centimetre how long it will take to travel 1.6 km

Answer 1

First convert wavelength from cm to m
$40cm =0.40m$
And distance from km to m
$1.6km = 1600m$
from Formula,
$c = fv \\ \: \: \: = 2 \times 0.40 \\ \: \: \: = 0.80ms {}^{ - 1}$
Thus the speed of the wave is 0.80 m/s
from Formula,
$time \: = d \div t \\ \: \: \: \: \: \: \: \: \: \: \: \: = 1600 \div 0.80 \\ \: \: \: \: \: \: \: \: \: \: \: \: = 16000 \div 8 \\ \: \: \: \: \: \: \: \: \: \: \: \: = 2000s$
thus
the answer is 2000 seconds

Answer 2

GIVEN:

υ = 2 Hz

λ = 40cm=40/100=0.4m

Speed of sound:
V= frequency * wavelength
= 2×0.4
⇒ 0.8 m/s

Distance = 1.6km = 1.6x1000m

Time = distance/ speed
⇒ 1.6x1000/ 0.8
⇒ 16×100/0.8

Therefore time required to travel 1.6 km is 2000 seconds.