Answer Happy

A straight railway track is at a distance ‘d’
from you. A distant train approaches you
travelling at a speed u (< speed of sound)
and crosses you. How does the apparent
frequency (f) of the whistle change with time
(f0 is the original frequency of the whistle).
Draw a rough f vs t graph.
(ii) A bat is tracking a bug. It emits a sound,
which reflects off the bug. The bat hears
the echo of the sound 0.1 seconds after it
originally emitted it. The bat can tell if the
insect is to the right or left by comparing
when the sound reaches its right ear to
when the sound reaches its left ear. Bat’s
ears are only 2 cm apart. Bats also use the
frequency change of the sound echo to
determine the flight direction of the bug.
While hovering in the air (not moving),
the bat emits a sound of 40.0 kHz. The
frequency of the echo is 40.4 kHz. Assume
that the speed of sound is 340 m/s.
(a) How far away is the bug?
(b) How much time delay is there between
the echo reaching the two ears if the bug
is directly to the right of the bat?