Newton's Contention

Q. The echo of a gun shot is heard 8 sec. after the gun is fired. How far from him is the surface that reflects the sound (velocity of sound in air = 350 m/s)

1. 700 m
2. 350 m
3. 1400 m
4. 2800 m

Q.

Does frequency affect wave speed?

Q. Consider a source of sound S and an observer P. The sound source is of frequency $n_0.$ The frequency observed by P is found to be $n_1$ if P approaches S at speed v and S is stationary ; $n_2$ if S approaches P at a speed v and P is stationary and, $n_3$ if each of P and S has speed v/2 towards one another. Now,

1. $n_1=n_2=n_3$
2. $n_1<n_2$
3. $n_3>n_0$
4. $n_3$ lies between $n_{1}and{n}_2$

Q.

What is speed of sound in air?

Q. A sound signal is simultaneously sent in air and water from a boat on a river. The echo of sound returned by the river bed is heard is $4\text{s}$, while the echo returned by the aeroplane is heard in $8\text{s}$. Find the distance between the aeroplane and the river bed.

[velocity of sound in air = $350\text{m/s}$, velocity of sound in water = $1500\text{m/s}$]

1. $8.8\text{km}$
2. $13.4\text{km}$
3. $4.4\text{km}$
4. $6.4\text{km}$

Q. Two tuning forks produce $4$ beats per second when they are sounded together. Now, both the forks are moved towards the observer at same speed $\left(u\right)$. The beat frequency now becomes $5\text{Hz}$. If the observer also begins to run with speed $u$ towards both the forks, what beat frequency will he hear now?

1. $4\text{Hz}$
2. $8\text{Hz}$
3. $6\text{Hz}$
4. $10\text{Hz}$

Q. A train is moving on a straight track with speed $20{\text{ms}}^{-1}$. It is blowing its whistle at the frequency of $1000\text{Hz}$. The percentage change in the frequency heard by a person standing near the track as the train passes him is close to:- (Speed of sound $=320{\text{ms}}^{-1}$)

1. $6\%$
2. $12\%$
3. $18\%$
4. $24\%$

Q.

The speed of sound in hydrogen at NTP is $1270{\mathrm{ms}}^{-1}$. Then the speed in a mixture of hydrogen and oxygen in the ratio of $4:1$ by volume will be:

1. $371{\mathrm{ms}}^{-1}$

2. $380{\mathrm{ms}}^{-1}$

3. $635{\mathrm{ms}}^{-1}$

4. $950{\mathrm{ms}}^{-1}$

Q.

The frequency $\mathrm{y}$ of a light wave is a function of its wavelength $\mathrm{x}$. is the function relating the wavelength of light to its frequency linear or nonlinear?

Q. A source of sound $S$ is moving with a velocity of $50\text{m/s}$ towards a stationary observer. The observer measures the frequency of the source as $1000\text{Hz}$. What will be the apparent frequency of the source when it is moving away from the observer after crossing him? (Take velocity of sound in air $350\text{m/s})$

1. $857\text{Hz}$
2. $1143\text{Hz}$
3. $750\text{Hz}$
4. $807\text{Hz}$

Q. How much (in $m{s}^{-1}$) is the change in velocity of sound in air due to $1^{o}C$ rise in temperature?

Q. The velocities of sound at the same temperature in two monoatomic gases of densities $p_1$ and $p_2$ are $v_1$ and $v_2$ respectively. If $p_1/p_2=4$, then the value of $v_1/v_2$ is

1. $\frac{1}{4}$
2. $2$
3. $\frac{1}{2}$
4. $4$

Q. Does the sound of an explosion travel faster than the sound produced by a humming bee?

1. True
2. False

Q. The frequency changes by $20\%$ as a source approaches a stationary observer with constant speed $v_s$. What would be the percentage change in frequency as the source recedes from the observer with the same speed? [Given, $v_s<<v$(velocity of sound)]

1. $14.3\%$
2. $16.7\%$
3. $30\%$
4. $10\%$

Q.

Mention the conditions which are required for the echo to be heard?

Q. The velocity of sound in air at ${25}^0$ C is approximately ___

Q. A man is running between two identical sources producing sound of same frequency as shown in figure. If beat frequency obtained by him is 2 then what will be the new beat frequency obtained by him if he doubles his speed

Q. The extension in a string obeying Hooke's law $v$ is $x$. The speed of sound in the stretched string is $v$. If the extension in the string is increased to $1.5x$, the speed of sound will be

1. $0.75v$
2. $1.22v$
3. $1.50v$
4. $0.61v$

Q. In deriving the speed of sound in air, Newton assumed that the wave travels in

1. Adiabatic condition
2. Isothermal condition
3. Isobaric condition
4. Isoclinic condition

Q. The echo of a gunshot is heard $8\text{s}$ after the gun is fired. How far from him is the surface that reflects the sound?

Velocity of sound in air $=350\text{m/s}$

1. $1400\text{m}$
2. $2800\text{m}$
3. $700\text{m}$
4. $350\text{m}$

Q.

At a prayer meeting, the disciples sing JAI-RAM JALRAM. The sound amplified by a loudspeaker comes back after reflection from a building at a distance of 80 m from the meeting. What maximum time interval can be kept between one JAI-RAM and the next JAI-RAM so that the echo does not disturb a listener sitting in the meeting. Speed of sound in air is $320m{s}^{-1}$.

Q.

Calculate the wavelength of a sound wave whose frequency is $220Hz$ and the speed is $440\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$ in a given medium.

Q. A police car with a siren of frequency 8 kHz is moving with uniform velocity 36 km/hr towards a tall building which reflects the sound waves. The speed of sound in air is 320 m/s. The frequency of the siren heard by the car driver is

1. 8.25 kHz
2. 7.75 kHz
3. 8.50 kHz
4. 7.50 kHz

Q. Two cars A and B depart simultaneously from the same position and in same direction on a straight road. A starts with constant velocity $22m/s$, while B starts with constant velocity of $42m/s$. The driver of car A hears a sound of frequency $352\text{Hz}$ emitted by car B after 10 s of start. Find the actual frequency of the sound as emitted by B. (given velocity of sound = 330 m/s)

1. $525\text{Hz}$
2. $280\text{Hz}$
3. $372\text{Hz}$
4. $450\text{Hz}$

Q. The relation between velocity of sound in gas $\left(v\right)$ and r.m.s velocity of molecules of gas $v_{r.m.s}$ is

1. $v=v_{r.m.s}(\gamma /3{)}^{1/2}$
2. $v_{r.m.s}=v(2/3{)}^{1/2}$
3. $v=v_{r.m.s}$
4. $v=v_{r.m.s}(3/\gamma {)}^{1/2}$

Q. Ultrasonic, infrasonic and audio waves travel through a medium with speeds $V_u,V_i$ and $V_a$ respectively then,

1. $V_u,V_i$ and $V_a$ are equal
2. $V_u>V_a>V_i$
3. $V_u<V_a<V_i$
4. $V_a<V_u$ and $V_u\approx V_i$

Q. According to Newton's formula, the speed of sound in air at STP is:
(Take the mass of $1$ mole of are is $29\times {10}^{-3}kg)$

1. $260m{s}^{-1}$
2. $270m{s}^{-1}$
3. $250m{s}^{-1}$
4. $280m{s}^{-1}$

Q. The ratio of speed of sound wave in Neon to that in H${}_2$ O vapors at any temperature is

1. $\frac{9}{8}$
2. $\frac{3}{2\sqrt{2}}$
3. $\frac{3}{2}$
4. $\frac{3}{\sqrt{10}}$

Q. An observer in a speeding car sees a traffic jam ahead of him. He slows down to $36\text{km/hour}$. He finds that traffic has eased. A car moving ahead of him at $18\text{km/hour}$ is honking at a frequency of $1392\text{Hz}$. If the speed of sound is $343\text{m/s}$, the frequency of the honk as heard by him will be

1. $1332\text{Hz}$
2. $1372\text{Hz}$
3. $1412\text{Hz}$
4. $1454\text{Hz}$

Q. According to Newton, when sound propogates in air, the temperature variation in the medium is

1. Zero
2. 10 C
3. 5 C
4. 1 C