Tag: physics

Questions Related to physics

Gas at a pressure ${P} _{0}$ is contained in a vessel. If the masses of all the molecules are halved and their speeds are doubled, the resulting pressure $P$ will be equal to

particles of a gas ideal gases physics

  1. $4{P} _{0}$

  2. $2{P} _{0}$

  3. ${P} _{0}$

  4. $\cfrac{{P} _{0}}{2}$

Show answer
Correct Option: B
Explanation:

$\begin{array}{l} P=\dfrac { 1 }{ 3 } \dfrac { { mN } }{ V } v _{ rms }^{ 2 } \ \therefore p\propto mv _{ rms }^{ 2 } \ so\, \dfrac { { { P _{ 2 } } } }{ { { P _{ 1 } } } } =\dfrac { { { m _{ 2 } } } }{ { { m _{ 2 } } } } \times { \left( { \dfrac { { { v _{ 2 } } } }{ { { v _{ 1 } } } }  } \right) ^{ 2 } } \ =\dfrac { { { m _{ 1 } }/2 } }{ { { m _{ 1 } } } } { \left( { \dfrac { { 2{ v _{ 1 } } } }{ { { v _{ 1 } } } }  } \right) ^{ 2 } } \ =2 \ { P _{ 2 } }=2{ P _{ 1 } } \ =2{ P _{ 0 } } \end{array}$

Hence,
option B is correct answer.

With increase in temperature, the density of a substance in general :

particles of a gas ideal gases physics

  1. increases

  2. decreases

  3. first increases then decreases

  4. first decreases then increases

Show answer
Correct Option: B
Explanation:

$Answer:-$ B

In general desity decreases with increase in temperature since $density=\dfrac{mass}{volume}$ 
Volume increases in general with increase in temperature and it is inversely proportional to density hence density decreases.
But for the case of water(when heated) it is different heating, its density first decreases and then increases.

When a drop of ink is put in a beaker of water

particles of a gas ideal gases physics

  1. Ink particle gradually move into the entire quantity of water and then get mixed the water

  2. Ink particles immediately mixes with water

  3. Ink particle moves as a lump cooling water in the process, and then mixes with the water

  4. Water mixes into ink particle and makes it colourless

Show answer
Correct Option: A
Explanation:

Due to motion of molecules of ink in water, it moves around the water and slowly mixes with water.Overall a diffusion process takes place between the particles of ink and particles of water.

Cooking gas containers are kept in a lorry moving with uniform speed. The temperature of the gas molecules inside will :

particles of a gas ideal gases physics

  1. increase

  2. decrease

  3. remain same

  4. decrease for some, while increase for others

Show answer
Correct Option: C
Explanation:

Since the pressure and volume of gas remains same , therefore , there will not be any change in the temperature of the gas molecules.

The phenomenon of browninan movement may be taken as an evidence of :

particles of a gas ideal gases physics

  1. kinetic theory of matter

  2. electromagnetic theory of radiation

  3. corpuscular theory of light

  4. photoelectric phenomenon

Show answer
Correct Option: A
Explanation:

Since brownian motion explains the collision between particles and their scattering, it is an evidence in support of kinetic theory of gases which is based on movement of particles in force fields of other particles and collision and scattering with them.

A hydrogen gas sample is contained in a cubical vessel of side $2 m$. A molecule of gas strike the wall of vessel at rate of $1000$ collisions/second. Sample contains $0.2 gm$ of Hydrogen. Number of molecules striking a wall per second is

particles of a gas ideal gases physics

  1. $5\times10^24$

  2. $2\times10^25$

  3. $2\times10^26$

  4. $5\times10^26$

Show answer
Correct Option: A

A drop of ink put in water illustrates

particles of a gas ideal gases physics

  1. Heating of molecules in a substance

  2. Stationary nature of molecules in a substane

  3. Motion of molecules in a substance

  4. Motion of substance in a molecule

Show answer
Correct Option: C
Explanation:

A drop of ink when poured in water gradually moves in the entire quantity of water and mixes to make the colour blueish.This is due to the diffusion of ink particles into the water particles.

Arrange in increasing order of greatest degree of freedom of motion:

particles of a gas ideal gases physics

  1. gas<solid

  2. Liquid< solid < gas

  3. Solid < liquid < gas

  4. Gas < liquid < solid

Show answer
Correct Option: C
Explanation:

Solids have least degree of freedom. Liquids have more degree of freedom and gases have least degree of freedom.Degree of motion is proportional to the extent upto which a molecule can move freely.

Why does glass break on sudden heating?

particles of a gas ideal gases physics

  1. All parts of glass expand equally

  2. All parts of glass don't expand equally

  3. High temperature makes a substance unstable

  4. Glasses are easy to break

Show answer
Correct Option: B
Explanation:

Pouring boiling water into a glass is highly likely to shatter it because the hot water contacts only a few part of the glass first whereas the other parts of the glass (such as the outside of the cup) remain cooler. The glass thus does not expand as a whole, but is pulled in different directions as part of it expands and part does not. This difference produces the shattering.

Hot water is poured on top of cold water. Gradually mixture attains same temperature. This happens because of 

particles of a gas ideal gases physics

  1. Instability

  2. Electrostatic attraction

  3. Gravitational force

  4. Motion of molecules in water

Show answer
Correct Option: D
Explanation:

Hot water mixes with cold water due to motion of water molecules and total volume attains same temperature.Overall a diffusion of particles take place between hot and cold water.