Exams › JEE Main › Physics

A whistle producing sound waves of frequencies 9500 Hz and above is approaching a stationary person with speed v m s⁻¹. The velocity of sound in air is 300 m s⁻¹. If the person can hear frequencies upto a maximum of 10,000 Hz, the maximum value of v upto which he can hear whistle is

1. 15√2 m s⁻¹
2. 15/√2 m s⁻¹
3. 15 m s⁻¹
4. 30 m s⁻¹

Correct answer: 15 m s⁻¹

Solution

The maximum frequency the person can hear is 10,000 Hz, and using the Doppler effect formula, we can determine the speed at which the whistle must be moving to produce this frequency when approaching the listener. By solving the equation, we find that the maximum speed v that allows the person to still hear the whistle is 15 m/s.

Related JEE Main Physics questions

• A sonometer wire of length ℓ has fundamental frequency f0. A bridge is placed at a point Δℓ away from the midpoint of the wire, where Δℓ is much smaller than ℓ. If the two resulting segments are made to vibrate in their fundamental modes, the number of beats produced is—
• Two identical piano wires are stretched with the same tension T. Each wire has a fundamental frequency of 600 Hz. If the tension of one wire is increased slightly, what fractional increase in tension is needed so that the two wires produce 6 beats per second when sounded together?
• Two sound sources, each producing waves of wavelength λ, are held at a fixed separation. An observer travels with speed u along the straight line joining the two sources. The beat frequency heard by the observer per second is
• A body of specific gravity ρ is suspended from a light steel wire. The wire supports transverse standing waves with a fundamental frequency of 300 Hz. The body is then placed in water such that exactly half of its volume is below the surface. What is the new fundamental frequency of the wire, in Hz?
• A transverse wave on a string has displacement y(x,t) = e^(-(ax² + bt² + 2abxt)). This corresponds to a:
• A sound source A emits waves of frequency 1800 Hz and is moving downward toward the ground with terminal speed v. An observer B standing on the ground directly below the source detects the sound at 2150 Hz. The frequency of the waves reflected back from the ground and received by source A is approximately: (Speed of sound = 343 m/s)

⚔️ Practice JEE Main Physics free + battle 1v1 →