When needed, use 340 m/s for the speed of sound and 3.00 x 108 m/s for the speed of light.

Question

A hiker determines the length of a lake by listening for the echo of her shout reflected by a cliff at the far end of the lake. She hears the echo 2.20 s after shouting. How long is the lake?

Answer 1

her shot travels down the lake, and the echo travels back
... total distance (and time) is two lake lengths

length = (2.20 s * 340 m/s) / 2