Advertisements
Advertisements
Question
A sitar wire is replaced by another wire of same length and material but of three times the earlier radius. If the tension in the wire remains the same, by what factor will the frequency change?
Solution
Frequency of vibrations produced by a stretched wire
`v = n/(2l) sqrt(T/n)`
Mass per unit length μ = `"Mass"/"Length"`
= `(pir^2 lp)/l`
= `pir^2p` ......[∵ M = vp = Alρ = πr2lρ]
∴ `v = n/(2l) sqrt(T/(pir^2ρ)`
⇒ `v ∝ sqrt(1/r^2)`
`v ∝ 1/r`
Hence, when the radius is tripled, v will be `1/3` rd of the previous value.
APPEARS IN
RELATED QUESTIONS
Answer briefly.
What is Doppler effect?
State the expression for apparent frequency when listener is stationary and source is moving towards the listener.
Answer briefly.
State the expression for apparent frequency when the source is stationary and the listener is
- moving towards the source
- moving away from the source
Discuss the following case-
Observer in motion and Source at rest.
- Observer moves towards Source
- Observer resides away from the Source
The speed of a wave in a certain medium is 900 m/s. If 3000 waves passes over a certain point of the medium in 2 minutes, then compute its wavelength?
A ship in a sea sends SONAR waves straight down into the seawater from the bottom of the ship. The signal reflects from the deep bottom bedrock and returns to the ship after 3.5 s. After the ship moves to 100 km it sends another signal which returns back after 2 s. Calculate the depth of the sea in each case and also compute the difference in height between two cases.
A railway engine whistling at a constant frequency moves with a constant speed aixi it goes past a stationary observer standing beside the railway track. Then the frequency of (n') of the sound heard by the observer with respect to time (t) can be best represented by which of the following curve?
A train, standing in a station yard, blows a whistle of frequency 400 Hz in still air. The wind starts blowing in the direction from the yard to the station with a speed of 10 m/s. Given that the speed of sound in still air is 340 m/s ______.
- the frequency of sound as heard by an observer standing on the platform is 400 Hz.
- the speed of sound for the observer standing on the platform is 350 m/s.
- the frequency of sound as heard by the observer standing on the platform will increase.
- the frequency of sound as heard by the observer standing on the platform will decrease.
The frequency of echo will be ______ Hz if the train blowing a whistle of frequency 320 Hz is moving with a velocity of 36 km/h towards a hill from which an echo is heard by the train driver. The velocity of sound in air is 330 m/s.
The observer is moving with velocity 'v0' towards the stationary source of sound and then after crossing moves away from the source with velocity 'v0'. Assume that the medium through which the sound waves travel is at rest. If v is the velocity of sound and n is the frequency emitted by the source, then the difference between apparent frequencies heard by the observer is ______.
