Question

A submarine in the sea, sends ultrasonic ping and a stopwatch is started simultaneously. The stopwatch stops on receiving the reflected wave from an obstacle and reads 1 minute 40 seconds. Calculate the distance of the obstacle from the submarine. (Speed of sound in water 1500 ms⁻¹.)

Answer 1

For an echo to occur,

Wave velocity = `"Total distance travelled"/"Time taken"`

1500 = `(2 xx "Distance")/100`

Distance = `(1500 xx 100)/2`

= `150000/2`

= 75000 m

= 75 km