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If More Air is Pushed in a Soap Bubble, the Pressure in It

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प्रश्न

If more air is pushed in a soap bubble, the pressure in it

पर्याय

  • decreases

  •  increases

  •  remains same

  • becomes zero.

MCQ
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उत्तर

 Excess pressure inside a bubble is given by:  \[P = \frac{4T}{r}\].

When air is pushed into the bubble, it grows in size. Therefore, its radius increases. An increase in size causes the pressure inside the soap bubble to decrease as pressure is inversely proportional to the radius. 

 
 
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पाठ 14: Some Mechanical Properties of Matter - MCQ [पृष्ठ २९८]

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एचसी वर्मा Concepts of Physics Volume 1 and 2 [English]
पाठ 14 Some Mechanical Properties of Matter
MCQ | Q 16 | पृष्ठ २९८

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संबंधित प्रश्‍न

Explain why Surface tension of a liquid is independent of the area of the surface


Explain why A drop of liquid under no external forces is always spherical in shape


A U-shaped wire is dipped in a soap solution and removed. The thin soap film formed between the wire and the light slider supports a weight of 1.5 × 10–2 N (which includes the small weight of the slider). The length of the slider is 30 cm. What is the surface tension of the film?


It is said that a liquid rises or is depressed in capillary due to the surface tension. If a liquid neither rises nor depresses in a capillary, can we conclude that the surface tension of the liquid is zero?


Find the surface energy of water kept in a cylindrical vessel of radius 6.0 cm. Surface tension of water = 0.075 J m−2.


The lower end of a capillary tube of radius 1 mm is dipped vertically into mercury. (a) Find the depression of mercury column in the capillary. (b) If the length dipped inside is half the answer of part (a), find the angle made by the mercury surface at the end of the capillary with the vertical. Surface tension of mercury = 0.465 N m−1 and the contact angle of mercury with glass −135 °.


A hollow spherical body of inner and outer radii 6 cm and 8 cm respectively floats half-submerged in water. Find the density of the material of the sphere.


How much amount of work is done in forming a soap bubble of radius r?


Obtain an expression for the capillary rise or fall using the forces method.  


A drop of oil placed on the surface of water spreads out. But a drop of water place on oil contracts to a spherical shape. Why?


Water rises in a capillary tube of radius r upto a height h. The mass of water in a capillary is m. The mass of water that will rise in a capillary of radius `"r"/4` will be ______.


A square frame of each side L is dipped in a soap solution and taken out. The force acting on the film formed is _____.
(T = surface tension of soap solution).


Two small drops of mercury each of radius 'R' coalesce to form a large single drop. The ratio of the total surface energies before and after the change is ____________.


Why is raindrop spherical in nature?


For a surface molecule ______.

  1. the net force on it is zero.
  2. there is a net downward force.
  3. the potential energy is less than that of a molecule inside.
  4. the potential energy is more than that of a molecule inside.

Is surface tension a vector?


This model of the atmosphere works for relatively small distances. Identify the underlying assumption that limits the model.


Surface tension is exhibited by liquids due to force of attraction between molecules of the liquid. The surface tension decreases with increase in temperature and vanishes at boiling point. Given that the latent heat of vaporisation for water Lv = 540 k cal kg–1, the mechanical equivalent of heat J = 4.2 J cal–1, density of water ρw = 103 kg l–1, Avagadro’s No NA = 6.0 × 1026 k mole–1 and the molecular weight of water MA = 18 kg for 1 k mole.

  1. Estimate the energy required for one molecule of water to evaporate.
  2. Show that the inter–molecular distance for water is `d = [M_A/N_A xx 1/ρ_w]^(1/3)` and find its value.
  3. 1 g of water in the vapor state at 1 atm occupies 1601 cm3. Estimate the intermolecular distance at boiling point, in the vapour state.
  4. During vaporisation a molecule overcomes a force F, assumed constant, to go from an inter-molecular distance d to d ′. Estimate the value of F.
  5. Calculate F/d, which is a measure of the surface tension.

A liquid flows out drop by drop from a vessel through a vertical tube with an internal diameter of 2 mm, then the total number of drops that flows out during 10 grams of the liquid flow out ______. [Assume that the diameter of the neck of a drop at the moment it breaks away is equal to the internal diameter of tube and surface tension is 0.02 N/m].


When one end of the capillary is dipped in water, the height of water column is 'h'. The upward force of 105 dyne due to surface tension is balanced by the force due to the weight of water column. The inner circumference of capillary is ______.

(Surface tension of water = 7 × 10-2 N/m)


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