MBOSE Class 11 Question Paper 2020 for Physics

Total No. of Printed Pages ––12 (2)
HS/XI/Sc/Ph/20

short answer questions of two marks each. Section C
2020
contains nine short answer questions of three marks
each. Section D contains one value based question of
PHYSICS
four marks and Section E contains three long answer
( Theory ) questions of five marks each.

Full Marks : 70
(e) There is no overall choice. However, an internal choice
Time : 3 hours has been provided in one question of two marks, one
question of three marks and all the three questions
The figures in the margin indicate full marks for the questions of five marks weightage. You have to attempt only one
choice in such questions.
General Instructions :

(a) 15 minutes time has been allotted to read this question (f) You may use the following values of standard physical
paper. The question paper will be distributed exactly constants wherever necessary.
15 minutes before the commencement of the
examination, the students will read the question paper (i) Acceleration due to gravity, g = 9.8 ms 2
only and will not write any answer on the remaining
empty spaces on the question paper during this period. (ii) Radius of the earth, Re = 6400 km

(b) All questions are compulsory. There are 30 questions (iii) Universal gas constant, R = 8.314J mol–1 K–1
in all.
(iv) Boltzmann constant, KB= 1.381 x 10–23 J K–1
(c) This question paper has five sections: Section A
(I and II) Section B, Section C, Section D and
(v) Velocity of light, C = 3 x 108ms–1
Section E.

(d) Section A–I contains five multiple choice questions of (vi) Young’s modulus of steel, Y = 2.0 x 1011Nm–2
one mark each, Section A–II contains very short answer
questions of one mark each. Section B contains seven (vii) Avogadro number, N = 6.023 x 1023 per gram mole.

HS/XI/Sc/Ph/20 HS/XI/Sc/Ph/20

(3) (4)

SECTION – A – I (c) 12 m/s

( Multiple choice questions ) (d) 14 m/s

1. The dimensional formula of gravitational constant is 1

(a) M1 L1 T 2 4. The centre of mass of a system shall be 1
(b) M0 L1 T 2 (a) at the centre of the system
(c) M 1 L3 T 2 (b) outside the system

(d) M 2 L3 T 1 (c) inside the system

(d) inside or outside the system
2. A man fires a bullet of mass 0.2 Kg with a speed of
5 m/s. The gun is of 1Kg mass. By what velocity does
the gun recoil backwards? 1

(a) 0.01 m/s 5. The displacement of a particle varies with time
according to the relation: 1
(b) 0.1 m/s
y  a sin t  b cos t
(c) 1 m/s

(d) 10 m/s (a) The motion is oscillatory but not S.H.M.

(b) The motion is S.H.M. with amplitude a + b
3. The position of an object moving along x-axis is given by,
x  a  bt 2 where a = 2m and b = 3 m/s 2 and t is (c) The motion is S.H.M. with amplitude a 2  b 2
measured in seconds. The velocity at t  2s is 1
(a) 2 m/s (d) The motion is S.H.M with amplitude a 2  b2

(b) 6 m/s

HS/XI/Sc/Ph/20 HS/XI/Sc/Ph/20

(5) (6)

SECTION – A–II 12. Either
( Very short answer type questions ) A body of mass 2.5 Kg is moving with a constant speed
of 45 m/s. A constant force is applied on the body
6. Can there be a physical quantity which has a unit but such that the speed changes to 15m/s in 10 seconds.
no dimensions? 1 The direction of motion of the body is unchanged
thoughout its motion. What is the magnitude and
direction of the force? 2
7. Why a cricketer moves his hands backwards while
holding a catch? 1 Or

A cyclist speeding at 5 m/s on a level road takes a
8. From your day to day experience, give an example in sharp circular turn of radius 3 m without reducing
which a couple of force is applied. 1 the speed. The coefficient of static friction between
the tyres and the road is 0.1. Will the cyclist slip taking
the turn? 2
9. Two identical solid balls, one of ivory and the other of
wet-clay, are dropped from the same height on the
floor. Which one will rise to a greater height after
striking the floor and why? 1 13. State work energy theorem. Hence derive its expression. 2

10. When will the motion of a simple pendulum be simple
harmonic? 1 14. A rope of negligible mass is wound round a hollow
cylinder of mass 3 Kg and radius 40 cm. What is the
angular acceleration of the cylinder if the rope is pulled
with a force of 30 N ? Given moment of inertia of the
SECTION – B
cylinder about its axis is 0.48 Kg m2. 2
( Short answer type I questions )

15. The mass m of a substance undergoes a change from
11. The centripetal force ( F ) acting on a particle moving one state to another on application of heat of quantity
uniformly in a circle may depend upon its mass (m), Q given by 2
velocity (v) and radius (r) of the circle. Derive the
formula for ‘F’ using the method of dimensions. 2 Q=mL

HS/XI/Sc/Ph/20 HS/XI/Sc/Ph/20

(7) (8)

What does L represent? Which parts of the following OR
graph does L represent? Show that motion in a plane can be treated as two
separate simultaneous one dimensional motions with
constant acceleration along two perpendicular

Temperature (oC)
E directions. 3
C
D
A B 19. State Newton’s Second Law of Motion. Hence, derive
the expression F = ma by calculus method where the
O
symbols have their usual meanings. 3

Heat (energy)

16. What happens to the internal energy of a gas during 2 20. Show that for an elastic collision of two bodies in one
(i) Isothermal expansion dimension, the relative velocity of approach is equal
to the relative velocity of separation. 3
(ii) Adiabatic expansion

17. Calculate rms velocity of oxygen molecule at 27oC 2 21. Either,
A ring, a disc and a sphere, all having the same radius
SECTION –– C and mass, roll down an inclined plane from the same
height. Which of these will reach the bottom first?
( Short answer type – II Questions )
Explain why. 3
OR
18. Either
Derive the equations of motion:- Define Moment of Inertia and radius of gyration. If
the moment of inertia of a thin rod of mass ‘M’ and
1 2 length ‘L’ about an axis through its centre and
(i) S  ut  at and
2
ML2
perpendicular to its lenght is , calculate its radius
(ii)  2  u 2  2as graphically 12
of gyration. 1+1+1=3
Where, the symbols have their usual meanings. 3

HS/XI/Sc/Ph/20 HS/XI/Sc/Ph/20

(9) ( 10 )

22. State and Prove Stoke’s law using dimensional 26. A boy pulls a string attached to a wooden block with a
analysis. 1+2=3 force of 30 N. The angle between the string and the
horizontal ground is 30o. How much is 3
(a) the effective value of the force that tends to move
23. (a) Define Young’s Modulus. the block along the ground

(b) A structural steel rod has a radius of 10 mm and (b) the quantity of force tending to lift the block
a lenght of 1.0 m. A 100 kN force stretches it vertically upward.
along its length. Calculate (i) stress and strain on
the rod. (Given Young’s modulus of steel rod is
2.0  1011 N/m2 ). 1+2=3 SECTION –– D
( Value based question )

24. Three vessels of equal capacity have gases at the same 27. During summers in India, one of the most common
temperature and pressure. The first vessel contains practice to keep cool is to make ice balls of crushed
Neon (monatomic), the second contains chlorine ice, dip it in flavoured sugar syrup and sip it. For this
(diatomic), and the third contains uranium a stick is inserted into crushed ice and is squeezed in
hexafluoride (polyatomic). the palm to make it into the ball. Equivalently in
winter, in those areas where it snows, people make
(a) Do the vessels contain equal number of molecules? snow balls and throw around. Explain the formation
of ball out of crushed ice or snow in the light of P–T
(b) Is the root mean square speed of the molecules
diagram of water. 4
same in three cases? Justify.
1+2=3
SECTION –– E
25. A bat emits ultrasonic sound of frequency 1000 kHz
( Long answer type )
in air. If this sound meets a water surface, what is the
wavelength of
28. Either
(a) the reflected sound?
State parallelogram law of vector addition. Find the
(b) the transmitted sound? (Given speed of sound in magnitude and direction of the resultant of two vectors
air is 340 m/s and in water is 1486 m/s). A and B in terms of their magnitudes and angle
1½ + 1½ = 3 between them. 1+4=5

HS/XI/Sc/Ph/20 HS/XI/Sc/Ph/20

( 11 ) ( 12 )

Or Or
What is projectile motion? Find an expression for the What is simple harmonic motion? Mention two of its
time of flight and horizontal range of a projectile characteristics. Show that the force acting on a particle
projected with a speed V and making an angle  with of mass ‘m’ in simple harmonic motion is proportional
respect to the horizontal direction. 1+2+2=5 to the displacement and is directed towards the mean
position. 1+1+3=5

29. Either
(a) Obtain an expression for acceleration due to 
gravity ‘g’ at a height above the surface of the
earth. Draw a graph showing the variation of ‘g’
with height. 3
(b) At what height above the earth’s surface, the
value of ‘g’ is half of its value on earth’s surface?
(Given R = 6400 km) 2
Or
(a) Derive an expression for escape velocity of an
object from the surface of a planet 3
(b) Using the expression for escape velocity from the
surface of the planet earth, calculate the numerical
value of escape velocity of a body of mass 10 kg
from the surface of the earth (R  6.4  10 6 m ) . 2

30. Either
(a) Derive the equation of the time period of a simple
pendulum. 3
(b) Show that the lenght of a second pendulum is
nearly 1 m. 2

HS/XI/Sc/Ph/20 HS/XI/Sc/Ph/20