Question 11 — A vehicle is fitted with - Questions at the end of the chapter - Chapter 10 - Sound Waves: Characteristics and Application (Exploration

Last updated at July 20, 2026 by

Question 11
A vehicle is fitted with an ultrasonic distance sensor as part of parking assistance system which provides echolocation, while the driver is reversing the vehicle. It emits ultrasonic wave (about 40 kHz) which is reflected by the obstacle. When the warning beep starts sounding at a distance of 1.2 m from the obstacle, how much time is taken by ultrasonic wave to travel to the obstacle and come back? Assume the speed of ultrasonic wave in air to be 345 m s⁻¹.
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  • Total path = to the obstacle and back =2× 1.2=2.4 m .
  • Time = distance speed = 2.4 345 ≈ 0.007 s (about 7 ms).
Parking Sensor Time Round trip = 2 times 1.2 = 2.4 m Time = distance divided by speed 2.4 / 345 is about 0.007 s
Back to: 10.8.1 Echolocation
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