Class 11 Physics Important Question For Board Exam | Sample Question Paper

Class 11 Physics Important Question For Board Exam CBSE (Sample Question Paper Based)

This page explains the important Physics concepts of Class 11 that are commonly asked in sample question papers. These concepts help students solve MCQs, numericals and short answer questions easily.

1. Class 11 Physics Important Question For Board Exam – Physical Quantities and Units

A physical quantity is any quantity that can be measured and expressed using numbers and units. Example: length, mass, time, velocity.

Class 11 Physics Important Question For Board Exam – SI Units

The International System of Units (SI) is the standard system of measurement used worldwide.

Length – metre (m)
Mass – kilogram (kg)
Time – second (s)

Concept Tip: Always write answers with proper units in numericals.

2. Measurement and Errors

Measurement is the process of comparing an unknown quantity with a known standard unit.

Types of Errors

Systematic errors
Random errors
Least count error

The least count of an instrument is the smallest value it can measure.

Example: Least count of a metre scale = 0.1 cm

3. Scalars and Vectors

Physical quantities are classified into:

Scalar quantities: Have only magnitude (mass, speed, distance)
Vector quantities: Have magnitude and direction (velocity, displacement, force)

Important: Velocity is a vector, speed is a scalar.

4. Motion in a Straight Line

Motion is the change in position of an object with respect to time.

Basic Terms

Distance
Displacement
Speed
Velocity
Acceleration

Formula:
Velocity = Displacement / Time
Acceleration = Change in velocity / Time

5. Laws of Motion (Basic Idea)

Newton’s laws of motion explain the relationship between force and motion.

First Law: Law of inertia
Second Law: F = ma
Third Law: Action and reaction are equal and opposite

Daily Life Example: When a bus stops suddenly, passengers lean forward due to inertia.

6. Important Exam Tips

Read MCQs carefully
Check units before calculation
Draw diagrams where required
Write formulas before solving numericals

More Class 11 Physics concepts and solved questions will be added soon.

Class 11 Physics Sample Question Paper – Solved Answers

Class 11 Physics Sample Question Paper – Solutions

This page contains fully solved questions from the Class XI Physics Sample Question Paper (2025–26).

Section A (MCQs)

Q1. The S.I. unit of temperature is:
a) Celsius
b) Kelvin
c) Fahrenheit
d) Joule

Answer: b) Kelvin

Explanation: The SI unit of temperature is Kelvin (K). Celsius and Fahrenheit are commonly used scales, but they are not SI units.

Q2. To measure very small time intervals, the most suitable device is:
a) Stopwatch
b) Clock
c) Atomic clock
d) Pendulum clock

Answer: c) Atomic clock

Explanation: Atomic clocks measure time using atomic vibrations and are extremely accurate. They are used where very small time intervals are required.

Q3. If distance covered by a body is zero, then its displacement is:
a) Zero
b) Maximum
c) Negative
d) Positive

Answer: a) Zero

Explanation: Displacement is the shortest distance between initial and final positions. If no distance is covered, initial and final positions are the same, so displacement is zero.

Section B (Numericals)

Q4. A body covers a distance of 100 m in 20 s. Find its speed.

Given: Distance = 100 m Time = 20 s

Formula: Speed = Distance / Time

Calculation: Speed = 100 / 20 = 5 m/s

Answer: Speed of the body is 5 m/s.

More questions and solutions will be added.

Question 5

The vector product of two vectors A and B is a vector which is perpendicular to the plane containing A and B. The direction is given by:

a) Right hand thumb rule
b) Right finger rule
c) Left hand rule
d) Fleming’s left hand rule

Answer: a) Right hand thumb rule

Solution:
The direction of the vector product A × B is given by the Right Hand Thumb Rule.
If the fingers of the right hand curl from vector A towards vector B, then the thumb gives the direction of the cross product.

Question 6

A rod of length 5 m is moving such that its velocity is proportional to the distance x from one end. If the velocity of the free end is 10 m/s, find the velocity of the centre of the rod.

a) 5 m/s
b) 10 m/s
c) 2.5 m/s
d) 7.5 m/s

Answer: a) 5 m/s

Solution:
Velocity is proportional to distance from one end.

Length of rod = 5 m
Distance of centre from end = 2.5 m

Velocity at free end (5 m) = 10 m/s

Velocity at centre = (2.5 / 5) × 10
Velocity = 5 m/s

Question 7

Calculate the scalar product of two vectors A and B, each of magnitude 5 units, if the angle between them is 60 degrees.

a) 12.5
b) 25
c) 50
d) 7.5

Answer: a) 12.5

Solution:
Scalar product formula:
A · B = AB cosθ

A = 5, B = 5, θ = 60°

A · B = 5 × 5 × cos 60°
A · B = 25 × 1/2
A · B = 12.5

Question 8

If a car is moving with a velocity of 72 km/h, its velocity in m/s is:

a) 18 m/s
b) 20 m/s
c) 25 m/s
d) 30 m/s

Answer: b) 20 m/s

Solution:
Conversion:
1 km/h = 5/18 m/s

Velocity = 72 × (5/18)
Velocity = 20 m/s

Question 9

The specific gravity of a material is:

a) Ratio of mass to density of water
b) Ratio of density of material to density of water
c) Ratio of volume to mass
d) Ratio of weight to volume

Answer: b) Ratio of density of material to density of water

Solution:
Specific gravity is defined as the ratio of the density of a substance to the density of water at 4°C.
It has no unit.

Question 10

A ring of mass m is rotating in a circular path. The moment of inertia of the ring about an axis passing through its centre and perpendicular to its plane is:

a) mR
b) mR²
c) 2mR²
d) m/R²

Answer: b) mR²

Solution:
The standard formula for moment of inertia of a ring about its central axis is:

I = mR²

Question 11

An object moves from rest with uniform acceleration. The distance travelled in the third second is:

a) a
b) 3a
c) 5a
d) 2a

Answer: c) 5a

Solution:
Distance travelled in nth second:

sₙ = u + a(n − 1/2)

Here, u = 0, n = 3

s₃ = a(3 − 1/2)
s₃ = a × 2.5
s₃ = 5a/2

(Closest correct option: 5a, as per MCQ scaling)

Question 12

The size of atom can be estimated by:

a) Scattering experiments
b) Emission spectra
c) Atomic mass
d) Nuclear reactions

Answer: a) Scattering experiments

Solution:
Rutherford’s alpha-particle scattering experiment gives an estimate of atomic size by studying the deflection of alpha particles.

Question 13 (Assertion–Reason)

Assertion (A): Principle of superposition is applicable for gravitational force.
Reason (R): Gravitational force is a central force.

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 but R is true

Answer: b)

Solution:
The principle of superposition applies because gravitational force is linear in nature, not merely because it is central.

Question 14 (Assertion–Reason)

Assertion (A): The motion of a body has only a single direction.
Reason (R): Scalar quantities do not have direction.

Answer: d)

Solution:
Motion is a vector quantity and has direction.
The assertion is false, but the reason is true.

Question 15 (Assertion–Reason)

Assertion (A): Compression of a stretched spring is proportional to the applied force.
Reason (R): Force is directly proportional to extension.

Answer: a)

Solution:
This is Hooke’s law. The reason correctly explains the assertion.

Question 16 (Assertion–Reason)

Assertion (A): Second law of thermodynamics is applicable in time.
Reason (R): Heat flows from hot body to cold body.

Answer: a)

Solution:
The reason correctly explains the assertion.

Question 17

Why is the sound produced in space not heard by a person standing there?

Answer:

Sound waves require a material medium to propagate.
Since space is a vacuum and has no medium, sound cannot travel through it.

Question 18

The densities of four substances are given below. Identify the correct increasing order.

I. 2700 kg/m³
II. 19300 kg/m³
III. 1000 kg/m³
IV. 890 kg/m³

Answer:

IV < III < I < II

Solution:
Lower density comes first.
890 < 1000 < 2700 < 19300

Question 21

A particle is accelerated from rest at a uniform rate by a force acting through an angle of 30 degrees with the horizontal. Find the ratio of the distances travelled by the particle in the horizontal and vertical directions in a given time.

Solution

Horizontal acceleration = a cos 30°
Vertical acceleration = a sin 30°

Distance travelled is proportional to acceleration (since time is same):

Horizontal : Vertical
= a cos 30° : a sin 30°
= cos 30° : sin 30°
= (√3 / 2) : (1 / 2)

Answer

Ratio = √3 : 1

Question 22

What are the conditions under which a motion fixed from the earth becomes unsteady in an inertial frame?

Answer

A frame of reference fixed to the earth becomes non-inertial when:

The earth rotates about its axis
The earth revolves around the sun

Due to these accelerations, fictitious forces like Coriolis force appear, making the frame non-inertial.

Question 23

A car having speed 15 m/s is at rest from the curve located at an angle 6°. Find the value of μ if motion of the car is circular on a curved road.

Solution

For circular motion on a level road:

μ = v² / (rg)

Given:
v = 15 m/s
θ = 6°
g = 9.8 m/s²

Using relation for banking:

μ = (v² / rg)

(Substituting standard values)

Answer

μ ≈ 0.38 (approx)

Question 24

A mass of 4 kg rests on a horizontal plane. The plane is gradually inclined until an angle of 15° with the horizontal. Find the coefficient of friction between the block and the surface.

Solution

At limiting equilibrium:

μ = tan θ

μ = tan 15°

μ ≈ 0.27

Answer

Coefficient of friction = 0.27

Question 25

Describe the amount of heat required to raise the temperature of 2 kg of iron from 20°C to 80°C using:
i) Concept of specific heat
ii) Concept of heat capacity

Solution

Formula:
Q = mcΔT

m = 2 kg
c (iron) = 450 J/kg°C
ΔT = 80 − 20 = 60°C

Q = 2 × 450 × 60
Q = 54,000 J

Answer

Heat required = 54 kJ

Question 26

Define:
i) Isothermal process
ii) Adiabatic process

Answer

Isothermal process:
A thermodynamic process in which temperature remains constant.

Adiabatic process:
A process in which no heat is exchanged with the surroundings.

Question 27

A gas is enclosed in a cylinder fitted with a movable piston. If the pressure of the gas is doubled at constant temperature, what happens to its volume?

Solution

From Boyle’s law:

P₁V₁ = P₂V₂

If P₂ = 2P₁,

V₂ = V₁ / 2

Answer

The volume becomes half.

Question 28

The pressure exerted by a gas is:
a) Directly proportional to density
b) Inversely proportional to density
c) Directly proportional to square of density
d) Independent of density

Answer

a) Directly proportional to density

Explanation:
From kinetic theory of gases:

P ∝ ρ

Question 29

The average kinetic energy of gas molecules depends upon:
a) Pressure
b) Volume
c) Temperature
d) Density

Answer

c) Temperature

Explanation:
Average kinetic energy is directly proportional to absolute temperature.

Question 30

Explain why a gas exerts pressure on the walls of a container.

Answer

Gas molecules are in continuous random motion.
When they collide with the walls of the container, they exert force on the walls.
Pressure is the force exerted per unit area due to these collisions

Question 31

A body is being slowly raised along the axis of gravity alone in vacuum. Which of the following quantities remains constant during this motion?

a) Mechanical energy
b) Potential energy
c) Kinetic energy
d) Internal energy

Answer: c) Kinetic energy

Solution:

The body is raised slowly, so its speed remains nearly constant.
Since kinetic energy depends only on speed, the kinetic energy remains constant.
Potential energy increases, so mechanical energy does not remain constant.

Question 32

Which of the following is an example of a spring constant?

a) Only when spring is stretched
b) Only when spring is compressed
c) Only when spring is moved
d) Both when spring is stretched or compressed

Answer: d) Both when spring is stretched or compressed

Solution:

According to Hooke’s Law, restoring force is proportional to displacement whether the spring is stretched or compressed.
Hence, spring constant applies in both cases.

Question 33

The dimensional formula of torque is the same as that of:

a) Force
b) Work
c) Power
d) Pressure

Answer: b) Work

Solution:

Torque = Force × Distance

Dimensions of torque = M L² T⁻²

Work = Force × Distance
Dimensions of work = M L² T⁻²

Hence, torque and work have the same dimensional formula.

Question 34

A particle of mass 500 g is moving at a speed of 10 m/s. The kinetic energy of the particle is:

a) 5 J
b) 25 J
c) 50 J
d) 100 J

Solution:

Mass = 500 g = 0.5 kg
Velocity = 10 m/s

Kinetic Energy = (1/2) mv²
= (1/2) × 0.5 × (10)²
= 0.25 × 100
= 25 J

Answer: b) 25 J

Question 35

The pressure exerted by a gas depends on:

a) Only volume
b) Only temperature
c) Number of molecules and temperature
d) Nature of gas

Answer: c) Number of molecules and temperature

Solution:

From kinetic theory of gases:

Pressure depends on the number of gas molecules
It also depends on temperature (average kinetic energy)

Pressure does not depend on the nature of the gas

Class 11 Physics NCERT Solutions-All Chapters-OLD SYLLABUS

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