The motion detectors in class use ultrasonic sound waves for echo location which travel 343 m/s in air. If it takes a sound wave 0.06 seconds to reach an object, how far away is it?

Answer 1

distance (d) = velocity(v) * time(t)

To help remember things like this, include the units:

d meters = v meters/sec * t sec

sec top and bottom cancel, so we are left with meters.

for the given problem:

d= 343 m/sec * 0.06 sec = 343*0.06 m

d = 20.58 m