Please refer to Class 11 Physics Sample Paper with solutions provided below. All sample papers for Physics Class 11 have been designed as per the latest paper pattern issued by CBSE for the current academic year. Students should practice these guess papers for Class 11 Physics as it will help them to gain more understanding of the type of questions that are expected to be asked in upcoming Class 11 Physics exams. Please click on the links below to access free CBSE Sample Papers for Class 11 Physics.

**SECTION – A**

**All questions are compulsory. In case of internal choices, attempt any one of them.**

**1. When are the displacement and velocity in the same direction in SHM?****Answer :** When a particle executing SHM is moving from mean position towards extreme position, then the displacement and velocity are in the same direction, i.e., away from the mean position.

**2. Write Hooke’s law.****Answer :** For small deformations the stress developed in the body is directly proportional to the strain of the body.

i.e., Stress ∝ Strain

Stress = K Strain

K = Stress/Strain

where, K = a constant, called modulus of elasticity

**OR****Is Hooke’s law applicable for all materials?****Answer :** No, Hooke’s law is not obeyed by all materials. There are some materials which do not exhibit this linear relationship.

**3. What is the ratio between the potential energy and the total energy of a particle executing SHM, when its displacement is 1/3 times of its amplitude?****Answer :**

**4. Write any four fundamental postulates of the kinetic theory of an ideal gas.****Answer : **(i) All gases consist of molecules. The molecules are rigid elastic spheres and identical in all respects for a given gas and different for different gases.

(ii) The size of a molecule is negligible as compared to the average distance between molecules.

(iii) The molecules are in a state of continuous random motion, moving in all directions with all possible velocities.

(iv) The molecules exert no force on each other or on the walls of the container except during collision.

**OR****At what temperature does all molecular motion cease ? Explain.****Answer :** All molecular motion ceases at absolute zero or at 0 K. According to the kinetic interpretation of temperature, internal energy of an ideal gas is purely kinetic,

**5. What are the differences between stationary waves and progressive waves?****Answer :**

statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is NOT the correct explanation of A

(c) A is true but R is false

(d) A is false and R is also false

**6. Assertion (A) : In simple harmonic motion, kinetic energy and potential energy become equal when the displacement is (1/ 2) times the amplitude.****Reason (R) : In simple harmonic motion, kinetic energy is zero when potential energy is maximum. **

## Answer

B

**7. Assertion (A) : The speed of sound in a gas is not affected by change in pressure provided the temperature of the gas remains constant.****Reason (R) : The speed of sound is inversely proportional to the square root of the density of the gas.**

## Answer

B

**SECTION – B**

**Case Study Based Question :**

**8.** Total number of co-ordinates require to describe completely the position and configuration of a dynamical system is known as the number of degrees of freedom to the system.

If we consider a system consisting of two particles, then each particle has three degree of freedom so that the number of degrees of freedom of both the particles is six. If the two particles remain at a fixed distance from each other, there is a definite relation between the two particles. Motion of a body as a whole from one point to another is called translation.

In equilibrium the total energy is equally distributed in all possible energy modes, with each mode having an average energy equal to (1/2) kT.

Each translational and rotational degree of freedom contributes (1/2) kT to the energy. Each vibrational frequency contributes

2 × (1/2) kT = kT energy since vibration has both kinetic and potential modes of energy.

For mono-atomic of a single molecule is E = 3/2 k_{B}T

For diatomic, KE of a single molecule E = 5/2 kT

**(i) The total internal energy of one mole of rigid diatomic gas is**

(a) 3/2 RT

(b) 7/2 RT

(c) 5/2 RT

(d) 9/2 RT

## Answer

C

**(ii) For diatomic gas, degree of freedom is**

(a) 6

(b) 5

(c) 3

(d) 3/2

## Answer

B

**(iii) The energy per mole per degree of freedom of an ideal gas is**

(a) 3/2 k_{B}T

(b) 1/2 k_{B}T

(c) 3/2 RT

(d) 1/2 RT

## Answer

A

**(iv) A vessel contains a mixture of 1 mole of oxygen and two moles of nitrogen at 300 K. The ratio of the rotational kinetic energy per O _{2} molecule to that per N_{2} molecule is**

(a) 1 : 2

(b) 2 : 1

(c) 1 : 1

(d) depends on the moment of inertia of the two molecules

## Answer

C

**(v) According to equipartition law of energy each particle in a system of particles have thermal energy E equal to**

(a) E = k_{B}T

(b) E = 1/2 k_{B}T

(c) E = 3 k_{B}T

(d) E = 3/2 k_{B}T

## Answer

D

**SECTION – C**

**All questions are compulsory. In case of internal choices, attempt anyone.**

**9. Why does velocity increase when water flowing in a broad pipe enters a narrow pipe?****Answer : **When water enters into a narrow pipe, the area of cross-section (A) decreases and consequently velocity (v) increases as Av = constant.

**OR****A small spherical ball of density r is gently released in a liquid of density s(r > s). Find the initial acceleration of the ball.****Answer :**

**10. A particle executing a simple harmonic motion has a period of 6 sec. What is the time taken by the particle to move from the mean position to half the amplitude, starting from the mean position ?****Answer :** Since the motion is started from the mean position, therefore displacement x of a particle executing SHM at any time t from its mean position is given by

**11. Two wires P and Q of same diameter are loaded as shown in the figure. The length of wire P is L m and its Young’s modulus is Y N m ^{–2}, while length of wire Q is twice that of P and its material has Young’s modulus half that of P. Compute the ratio of their elongation.**

**Answer : **

**OR****Let r is the density of a metal at normal pressure. Its density when it is subjected to an excess pressure P is p′. If B is the bulk modulus of the metal, then find the ratio p′/p.****Answer :**

**12. State two conditions of a reversible process.****Answer :** The process should take place very slowly, so that it satisfies the following conditions :

(i) The system should be in thermal equilibrium.

(ii) The system should be in chemical equilibrium.

**SECTION – D**

**All questions are compulsory. In case of internal choices, attempt any one.**

**13. By applying the first law of thermodynamics to isobaric process, obtain a relation between two specific heats of a gas.****Answer :** In an isobaric process, pressure remains constant. If an amount of heat dQ is supplied to one mole of a gas at constant pressure and its temperature increases by dT, then dQ = C_{p}dT

Here C_{P} is molar specific heat of the gas at constant pressure. Therefore, for an isobaric process, the first law of thermodynamics becomes

C_{p}dT = dU + PdV …(i)

From perfect gas equation it follows that

PdV = RdT and dU = C_{V}dT

In the eqn. (i), substituting the value of PdV and dU, we get

C_{P}dT = C_{V}dT + RdT; C_{P} = C_{V} + R

**14. A piece of ice with a stone in it floats on water taken in a beaker. When the ice melts completely, what will happen to level of water?****Answer :** Let m, M be the mass of stone and ice piece respectively. As ice piece with stone of mass (m + M) floats in water, so mass of water displaced is (m + M). If rw is the density of water, then volume of water displaced is

V = M+m/p_{w} …(i)

When the ice melts completely, there will be extra water of mass M and volume M/rw in the beaker. Now the stone will sink and will displace water equal to its volume (= m/p_{s}), where p_{s} is the density of stone. Thus the total volume of extra water obtained by melting of ice and displaced by sinking stone is

**OR****Water at a pressure of 2 × 10 ^{4} N m^{–2} flows at a speed of 2 m s^{–1} through a horizontal pipe of cross-sectional area 0.02 m^{2}. The cross-sectional area is reduced to 0.01 m^{2}. What is the pressure in the smaller cross-section of the pipe?**

**Answer :**

**SECTION – E**

**All questions are compulsory. In case of internal choices, attempt any one.**

**15. Briefly describe the construction of a calorimeter.****Answer :**

Calorimeter is a device used for measuring the quantities of heat. It consists of a cylindrical vessel of

copper provided with a stirrer. The vessel is kept inside a wooden jacket. The space between the calorimeter and the jacket is packed with a heat insulating material like glass wool, etc. Thus the calorimeter gets thermally isolated from the surroundings. The loss of heat due to radiation is further reduced by polishing the outer surface of the calorimeter and the inner surface of the jacket. The lid is provided with holes for inserting a thermometer and a stirrer into the calorimeter.

When bodies at different temperatures are mixed together in the calorimeter, heat is exchanged between the bodies as well as with the calorimeter. If there is no loss of heat to the surroundings, then according to the principle of calorimetry,

Heat gained by cold bodies = Heat lost by hot bodies This equation can be used to determine the specific heat and latent heat of different substances.

**OR****(a) The temperature of 200 g of water is to be raised from 24°C to 90°C by adding steam to it. The mass of the steam required for this purpose is****(b) 200 g of ice is mixed with 200 g of water at 100°C. What will be the final temperature of the mixture?****(c) Calculate the heat required to convert 3 kg of ice at –12°C kept in a calorimeter to steam at 100°C at atmospheric pressure.****[C _{water} = 4186 J/kg K, C_{ice} = 2100 J/kg K, L_{f(ice)} = 3.35 × 10^{5} J/kg, L_{f(steam)} = 2.256 × 10^{6} J/kg].**

**Answer :**

**16. Two strings A and B of same material are stretched by same tension. The radius of the string A is double the radius of string B. Transverse wave travels on string A with speed VA and on string B with speed VB. Find the ratio of V _{A} V_{B} .**

**Answer :**Velocity of transverse wave on a string is given by ;

**OR****(a) A progressive wave is represented by y = 12 sin (5t – 4x) cm. On this wave, how far away are the two points having difference of 90°?****(b) The equations of displacement of two waves are y _{1} = 10_{sin} {3πt + π/3} and y_{2} = 5[sin3πt + √3cos3πt]. Find the ratio of their amplitudes.**

**Answer :**