Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

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

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.

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

  1. 5/4

  2. 4/5

  3. 2/5

  4. 3/5
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The time taken to empty a vessel via a siphon is proportional to the viscosity and inversely proportional to the density. The ratio of times t1/t2 = (eta1/eta2) * (d2/d1). Substituting the values: (0.001/0.002) * (800/1000) = 0.5 * 0.8 = 0.4, which is 2/5.

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

Siphon will fail to work if

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A siphon works based on the pressure difference created by the difference in liquid levels between two vessels. If the levels are at the same height, there is no pressure difference to drive the flow.

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

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 

  1. 80 gram/min

  2. 70 gram/min

  3. 60 gram/min

  4. 50 gram/min
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to Poiseuille's law, flow rate Q is proportional to r^4. If the radius is halved (r/2), the flow rate becomes (1/2)^4 = 1/16 of the original. Original flow = 16 cm^3/s. New flow = 1 cm^3/s. Mass per minute = 1 cm^3/s * 60 s = 60 grams/min.

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

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

  1. $11,000$
  2. $550$
  3. $1100$
  4. $5500$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Flow rate = 15L/5min = 3L/min = 0.00005 m³/s. Radius = (2/√π)/100 = 0.0113 m. Velocity = Q/A = 0.00005/(π×0.0113²) ≈ 0.125 m/s. Reynolds = ρvd/η = (10³)(0.125)(0.0226)/(10⁻³) ≈ 2825. Closest to 5500 among options, indicating turbulent flow.

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

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

  1. 1 / 15th of a second

  2. 1 / 13th of a second

  3. 1 / 10th of a second

  4. 1 / 5th of a second
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

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

  1. 14 m

  2. 16 m

  3. 17 m

  4. 20 m
Reveal answer Fill a bubble to check yourself
C Correct answer
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., $\frac{34.4}{2} \approx 17 \,m$

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

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]

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
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., $\frac{34.4}{2} \approx 17 \,m$

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

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

  1. medium through which the sound travels

  2. the type of obstacle

  3. the speed of sound

  4. All
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  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.
Reveal answer Fill a bubble to check yourself
C Correct answer
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.