- #1
Daniiel
- 123
- 0
A bat is chasing an insect. if the bat, moving at 6m/s emits a 40kHz sound and receives back an echo at 40.4 kHz. What speed and direction is the insect moving? take the speed of sound to be 343m/sOkay sooo.
ive mucked around with this a fair bit
so i know before f'>f that, so the insect is moving towards the bat
f' = f( (v + Vd) / (v- Vs) )
so the bat is both the source and detector
i tried to write it in terms of the insect
so Vd = Vb - Vi
and Vs = Vb - Vi
so i get Vi = f( V + Vb) + f' ( -v + Vb) all over f + f '
which = 4.29 m/s
is that correct?
ive mucked around with this a fair bit
so i know before f'>f that, so the insect is moving towards the bat
f' = f( (v + Vd) / (v- Vs) )
so the bat is both the source and detector
i tried to write it in terms of the insect
so Vd = Vb - Vi
and Vs = Vb - Vi
so i get Vi = f( V + Vb) + f' ( -v + Vb) all over f + f '
which = 4.29 m/s
is that correct?
Last edited: