Tag: physics

Questions Related to physics

A liquid is contained in a vessel. The liquid-solid adhesive force is very as compared to the liquid. The shape of the liquid surface will be

intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

  1. Horizontal

  2. Vertical

  3. Concave

  4. Convex

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Correct Option: A
Explanation:

If the liquid solid adhesive force is same as that of liquid then the surface will be horizontal at zero angle of contact.

On a clean glass plate a drop of water spreads to form a thin layer whereas a drop of mercury remains almost spherical because

intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

  1. mercury is a metal

  2. density of mercury is greater than that of water

  3. cohesion of mercury is greater than its adhesion with glass

  4. cohesion of water is greater than its adhesion with glass

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Correct Option: C
Explanation:

Mercury remains spherical on a glass plate due to greater cohesive force between mercury molecules than adhesive force between mercury and glass plate.

A capillary tube of radius $0.25\ mm$ is submerged vertically in water so that $25\ mm$ of its length outside water. The radius of curvature of the meniscus will be $(T = 7.5\times 10^{-3} N/m)$.

intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

  1. $0.2\ mm$

  2. $0.4\ mm$

  3. $0.6\ mm$

  4. $0.8\ mm$

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Correct Option: C
Explanation:

$h= \dfrac{2T}{dgx}$

$h= \dfrac{2\times 7.5 \times {10}^-3} {1000 \times 10 \times d}$
$h=25mm$
$d= 0.6 mm$

The gas, which is present the most in air, is___

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. oxygen

  2. nitrogen

  3. carbon dioxide

  4. water vapour

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Correct Option: B
Explanation:

1) Nitrogen $-78$%

2) Oxygen $-21$%
3) Inert Nobel gases $-0.9$%
4) Several trace gases $-0.1$%
The above list the different number of gases in descending order. As per the list clearly Nitrogen is the gas present in most air.

Heat is associated with 

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. kinetic energy of random motion of molecules

  2. kinetic energy of orderly motion of molecules

  3. total kinetic energy of random and orderly motion of molecules

  4. kinetic energy of random motion in some cases and kinetic energy orderly motion in other.

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Correct Option: A
Explanation:

Heating up a substance excites the molecules of that substance making  the molecules moves vigorously thus giving velocity to the molecules and we know kinetic energy of a body is by the virtue of its motion.       

The kinetic energy of translation of $20gm$ of oxygen at $47^oC$ is (molecule wt. of oxygen is $32gm/mol $and $R=8.3J/mol/K$)

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. 2490 joules

  2. 2490 ergs

  3. 830 joules

  4. 124.5 joules

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Correct Option: A

What is an ideal gas?

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. One that consists of molecules

  2. A gas satisfying the assumptions of kinetic theory

  3. A gas having Maxwellian distribution of speed

  4. A gas consisting of massless particles

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Correct Option: B
Explanation:

An ideal gas is a gas which satisfying the assumptions of the kinetic energy.

Statement 1: The internal energy of a perfect gas is entirely kinetic and depends only on absolute temperature of the gas and not on its pressure or volume.
Statement 2: A perfect gas is heated keeping pressure constant and later at constant volume. For the same amount of heat the temperature of the gas at constant pressure is lower than that at constant volume.

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. Statement 1 is true, statement 2 is true and statement 2 is correct explanation of statement 1

  2. statement 1 is true, statement 2 is false

  3. Statement 1 is true, Statement 2 is true but Statement 2 is not the correct explanation of Statement 1

  4. Statement 1 is false, Statement 2 is true

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Correct Option: C

A body at a temperature of ${ 727 }^{ \circ  }C$ and having surface area ${ 5cm }^{ 2 }$ , radiated 300J of energy each minute. The emissivity (Given: boltzmann constant=$ 5.67\times { 10 }^{ -8 }{ Wm }^{ -2 }{ K }^{ -4 }$ is

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. e=0.2

  2. e=0.02

  3. e=0.18

  4. e=0.15

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Correct Option: A

The average pressure of an ideal gas is  

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. $\rho = (1/3)\, mn \, V^2 _{av}$

  2. $\rho = (1/2)\, mn \, V _{av}$

  3. $\rho = (1/4)\, mn \, V^2 _{av}$

  4. $\rho = (1/3)\, mn \, V _{av}$

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Correct Option: A