Physics Question? (1 Viewer)

[Zokunu]

A fruit bat uses echo location to navigate in the dark. A hovering bat emitted an ultrasonic sound wave of frequency 20 kHz. A return wave reflected from a large tree was detected by the bat 0.50 seconds after the original wave was sent. If the speed of sound in air is 340 m/s, how far away was the tree from the bat when it emitted the original wave?

THX

 

[Fizzy_Cyst]

If the bat detected the reflected wave after 0.5s, then that means it must take half that time to travel from the bat towards the tree and the other half of the time to travel back from the tree to the bat. (Sound wave must travel from the bat to the object it reflects off and then back to the bat)

Therefore use speed = distance/time

distance = speed x time

distance = 340 x 0.25 (time taken to get from bat to tree) = 85m


Note that the frequency of the sound wave is irrelevant and just there to distract you!

 

[Zokunu]

If the bat detected the reflected wave after 0.5s, then that means it must take half that time to travel from the bat towards the tree and the other half of the time to travel back from the tree to the bat. (Sound wave must travel from the bat to the object it reflects off and then back to the bat)

Therefore use speed = distance/time

distance = speed x time

distance = 340 x 0.25 (time taken to get from bat to tree) = 85m


Note that the frequency of the sound wave is irrelevant and just there to distract you!

mhm ok, thanks man