MBOSE Class 11 Question Paper 2018 for Physics

Total No. of Printed Pages ––11 (2)
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2018 Acceleration due to gravity, g = 9.8 m/s2

PHYSICS Gravitational constant, G = 6.67 x 10–11 Nm2 /kg2

( Theory )
Universal gas constant, R = 8.314J/mole/K

Full Marks : 70 Mechanical equivalent of heat, J = 4.186 J/cal
Time : 3 hours
Avogadro number, N = 6.022 x 1023 /mole
The figures in the margin indicate full marks for the questions
Boltzmann constant, k = 1.381 x 10–23 J/mole/K
General Instructions :

(i) All questions are compulsory.

(ii) Marks for each question are indicated against it.
GROUP ––A
(iii) There is no overall choice. However, an internal choice
has been provided in two questions of two marks each, ( Multiple choice type questions )
two questions of three marks each and two questions
of five marks. Choose and write the correct answer in the answer script.
1 8  4
2
(iv) Use of ordinary calculator is allowed.
1. The dimensional formula [ML2 T –2] represents ½
(v) Mobile phones are not allowed in the Examination Hall.
(a) Moment of force
(vi) Use the following values of physical constants wherever
(b) Force
necessary:
(c) Acceleration
24
Mass of the earth, M = 6.00 x 10 kg
(d) Momentum
6
Radius of the earth, Re = 6.4 x 10 m

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2. Light year is the unit of ½ 5. The spherical shape of a small water droplet is due to
its ½
(a) Time
(a) friction
(b) Intensity of light
(b) viscosity
(c) Distance
(c) surface tension
(d) Energy
(d) density

3. In 1.0 second, a particle goes from point A to point B
moving in a semi-circle of radius 1.0m as shown in fig.
The magnitude of average velocity is 6. Due to capillarity action, a liquid will rise in a tube, if
½ the angle of contact is
A
½
(a) 3.14 m/s
(a) acute
(b) 2.0m/s

(c) 1.0 m/s 1.0m (b) obtuse

(d) Zero B (c) 900

(d) zero
4. To break a wire of 1mm radius, a force of 10 N is
required. To break a wire of 3 mm radius, the required
force will be. 7. The equation:
½
Area x Velocity = constant is called ½
(a) 90 N
(a) Bernoulli’s equation
10
(b) N
3 (b) Stoke’s equation
10 (c) Equation of continuity
(c) N
9
(d) Reynold’s number
(d) 30N

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(5) (6)

8. A car travels first half of the distance between two places 12. What is pressure head? 1
with a speed of 40 km/hr and the second half distance
with a speed of 60 km/hr. The average speed of the
13. Find the effective length of a second’s pendulum. 1
car is– ½
(a) 50 km/hr
14. What is the range of frequency of audible sound? 1
(b) 48 km/hr
15. Which of the three types of elasticity (Y, K, η ) is
(c) 100 km/hr possessed by all the three states of matter (solid, liquid,
gas)? 1
(d) 25 km/hr

16. Give one example each of conservative and non-
conservative forces. ½+½=1
GROUP – B
( Very short answer type questions )
GROUP –– C
Answer the following questions in a few words / sentences.
1 8  8 ( Short answer type –I questions )
9. An elastic wire is cut to half its original length. How
would it affect the maximum load the wire can support? 1
Answer the following questions within 30 words each:
2  8  16
10. A body is projected horizontally from a height of 10m,
with a speed of 9.8m/s. After what time of its projection, 17. Verify whether the following equation is dimensionally
will the horizontal and vertical components of velocities correct: 2
be equal? 1
V 2  U 2  2as
Where the symbols have their usual meanings.
11. A ball is thrown upwards with a velocity of 100 m/s.
How much time it will take to reach the ground.
18. Is the flying of a bird an example of parallelogram law
(Take g =10 m/s2) 1
of addition of vectors? Explain ½ + 1½ = 2

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19. If the distance (in meter) travelled by a body in time 24. A steel rod 100cm long is clamped at its middle. The
t (second) is given by 2 fundamental frequency of longitudinal vibrations of the
x  3t  6t 2 rod is given to be 2.53 kHz. What is the speed of sound
in steel? 2
then what will be the acceleration of the body?

Either GROUP –– D

20. What is friction? Why is it called a self adjusting force? ( Short answer type – II questions )
1+1=2
Or
Answer the following questions in 30 to 40 words each :
Define instantaneous power. Show that 2 3  9  27
 
P  F.v 25. Obtain an expression for the position vector of the
where symbols have their usual meanings. centre of mass of a system consisting of two particles. 3

21. An aircraft executes a horizontal loop of radius 1km
Either,
with a steady speed of 900km/h. Compare its
centripetal acceleration with the acceleration due to
26. Two vectors are inclined at an angle  . Find magnitude
gravity. 2 and direction of resultant vector. 3

Either, Or

22. An ideal gas is compressed at constant temperature. What is position vector and displacement vector?
Will its internal energy increase or decrease? Explain. 2 Distinguish between them with illustration.

Or

Define isothermal change. Write the expression for work 27. The relation between the displacement x and the time
done during an isothermal change. 1+1=2 ‘t’ of a particle moving under constant force is t  x  3,
where x is in metre and t in seconds. Determine (i) the
displacement of the particle at the instant when velocity
23. Calculate the r.m.s. velocity of oxygen molecules at is zero (ii) work done by the force in first 6 seconds.
S.T.P., the molecular weight of oxygen being 32. 2 1½ + 1½ = 3

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(9) ( 10 )

28. Establish the relation between torque and angular GROUP –– E
acceleration. Hence define moment of inertia. 2+1=3

( Long Answer type questions )
29. Two ball bearings each of mass ‘m’ moving in opposite
directions with equal velocities v collide head on with
each other. Predict the outcome of the collision, Answer the following questions in 70 to 80 words each :
assuming it is perfectly elastic. 3 5  3  15

30. Explain the principle of working of a heat engine with Either,
diagram. Define its efficiency. 2+1=3

34. State and explain Newton’s second law of motion. Show
Either, that Newton’s second law of motion is the real law of
motion. 2+3=5
31. Why and how Laplace corrected Newton’s formula for
velocity of sound in gas? 3
Or
Or
What are beats? Show the formation of beats
Explain with the help of a neat diagram, how banking
graphically. 1+2=3
provides the centripetal force necessary for a car to go
in a circular track. 1+4=5
32. State three assumptions of kinetic theory of gases. 3

33. Prove that for a harmonic oscillator (a massless loaded
spring). 3 35. Define escape velocity? Prove that the velocity of escape
of a body from the earth’s surface is 2 times the
1 Spring factor orbital velocity of a satellite revolving close to the

2 inertia factor surface of earth. 1+3+1=5

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Either,

36. (a) What is Stoke’s law? Derive the relation by the
method of dimensions. ½ + 2 = 2½
(b) Show that the terminal velocity ( ) of a sphere of
radius (r), density (  ) falling vertically through a
viscous fluid of density (  ) and coefficient of
viscosity (  ) is given by 2½

2 (    )r 2g
  
9 

Or

Define with example, capillarity and angle of contact.
Derive an expression for the ascend of a liquid in a
capillary tube.



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