Tag: physics

Questions Related to physics

A large bottle is fitted with a capillary siphon. Ratio of times taken to empty the bottle when it is filled with (i) water (ii) petroleum of relative density 0.8.

$( _{water} = 0.001poise, _{petroleum} = 0.002 poise, d _{water} = 1000 kg/m^3)$

physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. 5/4

  2. 4/5

  3. 2/5

  4. 3/5

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Correct Option: C

Siphon will fail to work if

physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. the densities of the liquid in the two vessels are equal

  2. the level of the liquid in the two vessels are at the same height

  3. both its limbs are of unequal length

  4. the temperature of the liquids in the two vessels are the same

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Correct Option: B

A ${ 16cm }^{ 3 }$ volume of water flows per second through a capillary tube of radius r cm and of length 1 cm, when connected to a pressure head of h cm of water. If a tube of the same length and radius r/2 is connected to the same pressure head, find the mass of water flowing per minute through the tube 

physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. 80 gram/min

  2. 70 gram/min

  3. 60 gram/min

  4. 50 gram/min

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Correct Option: C

If it takes $5$ minutes to fill a 15 litre bucket  from a water tap of diameter $\frac{2}{\sqrt{\pi}}$ cm then the Reynolds number for the flow is (density of water = $10^3 kg/m^3$ and viscosity of water = $10^{-3}$Pa.s) close to

physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. $11,000$

  2. $550$

  3. $1100$

  4. $5500$

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Correct Option: D

An echo of the sound produced can be heard only if it reaches our ear after -

physics acoustics conditions for hearing echo echo reflection of sound and echo ultrasound and its applications

  1. 1 / 15th of a second

  2. 1 / 13th of a second

  3. 1 / 10th of a second

  4. 1 / 5th of a second

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Correct Option: C
Explanation:

An echo is the repetition of sound that results as a reflection from a surface. An echo of the sound produced can be heard only if it reaches our ear after 1 / 10th of a second. This is due to the persistence of sound.

We can hear echoes only near the mountains. True or false.

physics acoustics conditions for hearing echo echo reflection of sound and echo ultrasound and its applications

  1. True

  2. False

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Correct Option: B
Explanation:

we can hear echoes anywhere, where the distance between the source and the point of reflection is sufficient enough.

In order to produce an echo, the minimum distance between the source of the sound and the reflecting body should be :

physics study of sound conditions for hearing echo echo reflection of sound and echo ultrasound and its applications

  1. 14 m

  2. 16 m

  3. 17 m

  4. 20 m

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Correct Option: C
Explanation:

As the sensation of sound persists in our brain for about 0.1 s, to hear a distinct echo the time interval between the original sound and the reflected one must be at least 0.1 s. If we take the speed of sound to be 344 m/s at a given temperature, say at 22 $^0C$ in air, sound must go to the obstacle and reach back the ear of the listener on reflection after 0.1s.
 
Hence, the total distance covered by the sound from the point of generation to the reflecting surface and back should be at least (344 m/s) ×0.1 s = 34.4 m. Thus, for hearing distinct echoes, the minimum distance of the obstacle from the source of sound must be half of this distance. I.e., $\frac{34.4}{2} \approx 17 \,m$

The minimum distance between the source of a sound and reflecting body should be 17 m for the formation of an echo. True or false

[consider the medium to be air]

physics study of sound conditions for hearing echo echo reflection of sound and echo ultrasound and its applications

  1. True

  2. False

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Correct Option: A
Explanation:

As the sensation of sound persists in our brain for about 0.1 s, to hear a distinct echo the time interval between the original sound and the reflected one must be at least 0.1 s. If we take the speed of sound to be 344 m/s at a given temperature, say at 22 $^0C$ in air, sound must go to the obstacle and reach back the ear of the listener on reflection after 0.1s.
 
Hence, the total distance covered by the sound from the point of generation to the reflecting surface and back should be at least (344 m/s) ×0.1 s = 34.4 m. Thus, for hearing distinct echoes, the minimum distance of the obstacle from the source of sound must be half of this distance. I.e., $\frac{34.4}{2} \approx 17 \,m$

The time gap between the two sounds-direct and echo depends upon:

physics acoustics conditions for hearing echo echo reflection of sound and echo ultrasound and its applications

  1. medium through which the sound travels

  2. the type of obstacle

  3. the speed of sound

  4. All

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Correct Option: A
Explanation:

The time gap between the two sounds-direct and echo depends upon the medium through which the sound travels. These two sounds can be heard distinctly provided the Distance between the observer and the reflecting surface is large enough to allow the reflected sound to reach him without interfering with the direct sound.

The direct sound and the echo can be heard differently provided:

physics acoustics conditions for hearing echo echo reflection of sound and echo ultrasound and its applications

  1. Distance between the observer and the reflecting surface is large enough to allow the reflected sound to reach him interfering with the direct sound.

  2. Distance between the obstacle and the source is small enough to allow the reflected sound to reach him interfering with the direct sound.

  3. Distance between the observer and the reflecting surface is large enough to allow the reflected sound to reach him without interfering with the direct sound.

  4. Distance between the obstacle and the reflecting surface is large enough to allow the reflected sound to reach him interfering with the direct sound.

Show answer
Correct Option: C
Explanation:

The time gap between the two sounds-direct and echo depends upon the medium through which the sound travels. These two sounds can be heard distinctly provided the Distance between the observer and the reflecting surface is large enough to allow the reflected sound to reach him without interfering with the direct sound.