An operator sitting in his base camp sends a sound signal of frequency 400 Hz. The signal is reflected back from a car moving towards him. The frequency of the reflected sound is found to be 410 Hz. Find the speed of the car. Speed of sound in air = 324 m s^-1.

A person standing on a road sends a sound signal to the driver of a car going away from him at a speed of 72 km h^-1. The signal travelling at 330 m s^-1, in air and having a frequency of 1600 Hz gets reflected from the body of the cur and returns. Find the frequency of the reflected signal as heard by the person.

A car moves with a speed of 54 km h” towards a cliff. The horn of the car emits sound of frequency 400 Hz at a speed of 335 m s^-1. (a) Find the wavelength of the sound emitted by the horn in front of the car. (b) Find the wavelength of the wave reflected from the cliff. (c) What frequency does a person sitting in the car hear for the reflected sound wave? (d) How many beats does he hear in 10 seconds between the sound coming directly from the horn and that coming after the reflection?

Figure (16-E12) shows a source of sound moving along the X-axis at a speed of 22 m s continuously emitting a sound of frequency 2-0 kHz which travels in air at a speed of 330 m s^-1. A listener Q stands on the Y-axis at a distance of 330 m from the origin. At t = 0, the source crosses the origin P. (a) When does the sound emitted from the source at P reach the listener Q? (b) What will be the frequency heard by the listener at this instant? (c) Where will the source be at this instant?

A source emitting sound at frequency 4000 Hz, is moving along the Y-axis with a speed of 22 m s^-1, A listener is situated on the ground at the position (660 m, 0). Find the frequency of the sound received by the listener at the instant the source crosses the origin. Speed of sound in air = 330 m s^-1.