#### Half Yearly Model Question Paper 2019

11th Standard

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Physics

Time : 02:30:00 Hrs
Total Marks : 70

Part I

Choose the most suitable answer from the given four alternatives and write the option code with the corresponding answer.

15 x 1 = 15
1. One of the combinations from the fundamental physical constants is ${{hc}\over{G}},$ The unit of this expression is

(a)

Kg2

(b)

m3

(c)

S-1

(d)

m

2. How many light years make 1 parsec?

(a)

3.26

(b)

6.67

(c)

1.5

(d)

9.4

3. A car moves from X to Y with a uniform speed Vn and returns to Y with a uniform speed VThe average speed for this round trip is

(a)

$\sqrt{V_uV_d}$

(b)

$\frac{V_uV_d}{V_d+V_u}$

(c)

$\frac{V_u+V_d}{2}$

(d)

$\frac{2V_dV_u}{V_d+V_u}$

4. The centrifugal force appears to exist

(a)

only in inertial frames

(b)

only in rotating frames

(c)

in any accelerated frame

(d)

both in inertial and non-inertial frames

5. A body of mass 5 kg explodes at rest into three fragments with masses in the ratio 1 : 1 : 3. The fragments with equal masses fly in mutually perpendicular directions with speeds of 21 m/s. The velocity of heaviest fragment in m/s will be

(a)

7$\sqrt { 2 }$

(b)

5$\sqrt { 2 }$

(c)

3$\sqrt { 2 }$

(d)

$\sqrt { 2 }$

6. A particle which is constrained to move along x-axis, is subjected to a force in the same direction which varies with the distance x of the particle from the origin as F(x) =kx + ax3. Here, k and a are positive constants. For x≥0, the functional form of the potential, energy U(x) of the particles

(a)

(b)

(c)

(d)

7. Which of the following is not a perfectly inelastic collision?

(a)

Striking of two glass bulbs

(b)

Bullet striking a bag and sand

(c)

An electron captured by a proton

(d)

A man jumping onto a moving cart

8. The center of mass of a system of particles does not depend upon,

(a)

position of particles

(b)

relative distance between particles

(c)

masses of particles

(d)

force acting on particle

9. A rod of length is 3 m and its mass acting per unit length is directly proportional to distance x from one of its end then its centre of gravity from that end will be at

(a)

1.5 m

(b)

2 m

(c)

2.5 m

(d)

3.0 m

10. If the distance between the Earth and Sun were to be doubled from its present value, the number of days in a year would be

(a)

64.5

(b)

1032

(c)

182.5

(d)

730

11. A satellite is moving around the Earth with speed v in a circular orbit of radius r. If the orbit radius is decreased by 1% its speed will _______.

(a)

increase by 1%

(b)

increase by 0.5%

(c)

decrease by 1%

(d)

decrease by 0.5%

12. The pressure of the Earth's atmosphere at sea level is due to the _________.

(a)

gravitational attraction of the Earth for the atmosphere

(b)

evaporation of water from the seas and oceans

(c)

fact that most living things constantly breathe air

(d)

heating of the atmosphere by the Sun

13. A distant star emits radiation with maximum intensity at 350 nm. The temperature of the star is

(a)

8280 K

(b)

5000K

(c)

7260 K

(d)

9044 K

14. A particle executing SHM has an acceleration of 64 cm/s2 with its displacement is 4 cm. Its time period, in seconds is ________.

(a)

$\frac{\pi}{2}$

(b)

$\frac{\pi}{4}$

(c)

$\pi$

(d)

2$\pi$

15. Which of the following options is correct?.

 A B (1) Quality (A) Intensity (2) Pitch (B) Waveform (3) Loudness (C) Frequency

Options for (1), (2) and (3), respectively are

(a)

(B),(C) and (A)

(b)

(C), (A) and (B)

(c)

(A), (B) and (C)

(d)

(B), (A) and (C)

16. Part II

Answer any 7 questions. Question no. 24 is compulsory.

7 x 2 = 14
17. What are types of discoveries in physics?

18. If $\vec A=3\hat i+4\hat j$ and $\vec B=7\hat i+24\hat j$ , find a vector having the same magnitude as $\vec B$ and parallel to $\vec A$.

19. Write the relation between angular momentum and rotational kinetic energy. Draw a graph for the same. For two objects of same angular momentum, compare the moment of inertia using the graph.

20. Calculate moment of inertia with respect to rotational axis xx' in following figures (a) and (b).

21. Two bodies of masses m and 4m are placed at a distance r. Calculate the gravitational potential at a point on the line joining them where the gravitational field is zero.

22. What do you mean by weight of a body? Is it a scalar or vector?

23. Explain the classification of longitudinal strain?

24. A piece of wood of mass m is floating erect in a liquid whose density is ρ. If it is slightly pressed down and released, then executes simple harmonic motion. Show that its time period of oscillation is

25. What is meant by an echo?. Explain.

26. Part III

Answer any 7 questions. Question no. 33 is compulsory.

7 x 3 = 21
27. Calculate the number of times a human heart beats in the life of 100 years old man. Time of one heart beat = 0.8s.

28. Figure shows the position-time graph of a particle of mass 4 kg. What is the

(a) Force on the particle for t < 0, t > 4s, 0 < t < 4s?
(b) Impulse at t = 0 and t = 4s?
(Consider one dimensional motion only)

29. A vehicle of mass 1250 kg is driven with an acceleration 0.2 along a straight level road against an external resistive force 500 N. Calculate the power delivered by the vehicle's engine if the velocity of the vehicle is 30 ms-1.

30. Find Torque about an Axis.

31. Two heavy spheres, each of mass 100kg and radius 0.8m are placed 1m about on a table What is the gravitational force and potential at the mid point of the line joining the centers of the spheres?

32. A light rod of length 2m is suspended horizontally by means of 2 vertical wires of equal lengths tied to its ends. One of the wires is made of steel & is of cross section A1 = 0.1 cm2 & other of brass &. is of cross section A2 = 0.2cm2, find out the position along the rod at which a weight must be suspended to produce (i) equal stresses in both wires, (ii) equai strains in both wires for steel, y = 20 x 1010 Nm-2 & for brass y =10 x 1010 Nm-2.

33. Write the important properties of thermal radiations.

34. Explain in detail the Maxwell Boltzmann distribution function.

35. Consider two organ pipes of same length in which one organ pipe is closed and another organ pipe is open. If the fundamental frequency of closed pipe is 250 Hz. Calculate the fundamental frequency of the open pipe.

36. Part IV

5 x 5 = 25
1. Consider a particle undergoing simple harmonic motion. The velocity of the particle at position x1 is v1 and velocity of the particle at position x2 is v2. Show that the ratio of time period and amplitude is
$\frac { T }{ A } =2\pi \sqrt { \frac { { x }_{ 2 }^{ 2 }-{ x }_{ 1 }^{ 2 } }{ { { v }_{ 1 }^{ 2 }x }_{ 2 }^{ 2 }-{ { v }_{ 2 }^{ 2 }x }_{ 1 }^{ 2 } } }$

2. Write short notes on reflection of sound waves from plane and curved surfaces.

1. Distinguish between isothermal and adlabatlc process.

2. Find the adiabatic exponent $\gamma$ for mixture of μ1 moles of monoatomic gas and μ2 moles of a diatomic gas at normal temperature

1. Drive the relation between g & Gravitational constant.

2. If a ball of skeel (density p =7.8 g cm-3) attains a terminal velocity of 10cm S-1 when falling in a tank of water (coefficient of viscosity) water = 8.5 x 10-4pa s. What will the terminal velocity in glycerine (P = 1.2 g cm-3,η = 13.2 ρa.s) be?

1. Explain the principle of homogeniety of dimensions. What are its uses? Give example

2. Write an expression for the kinetic energy of a body in pure rolling.

1. Write note on integration.

2. Arrive at an expression for power and velocity. Give some examples for the same.