MODEL QUESTION PAPER CLASS XI PHYSICS

TIME: 3HRS. MAX. MARKS 70

General Instructions:

1. All questions are compulsory. There are 26 questions in all. 2. This question paper has five sections: Section A, B, C, D and E. 3. Section A contains five questions of one mark each. Section B contains five questions of two marks each, Section C contain twelve questions of three marks each, Section D contains one value based question of four marks and Section E contains three questions of five marks each. 4. There is no overall choice. However, an internal choice has been provided in one question of two marks, one question of three marks and all the three questions of five marks weightage. You have to attempt only one of the choices in such questions.

Section-A

1. A body is travelling in a straight line with a uniformly increasing speed. Plot a graph which represents the change in distance (s) travelled with time (t). 2. A pebble of mass 0.05 kg is thrown vertically upward Give the direction and magnitude of the net force on the pebble, at the highest point where it is momentary at rest. (g = 10 ms–2). 3. Write dimensional formula for compressibility.

4. The pressure is increased on a gas, then what would be its effect of the

viscosity? 5. Two stars radiate maximum energy at wavelength 3.6×10–7m and 4.8×10–

7 m respectively. What is the ratio of their surface temperatures? Section-B

6. The bob of a pendulum is released from a horizontal position. If the length of the pendulum is 1m what is the speed with which the bob arrives at the lower most point given that it dissipates 10% of its initial energy against air resistance. (g = 10 ms–2) 7. Draw the graph showing the variation of acceleration due to gravity with (a) height above the earth’s surface. (b) depth below the earth’s surface

8. Find the torque of a force (7iˆ + 3jˆ − 5kˆ)N about the origin, The force acts on a particle whose position vector is (iˆ − jˆ + kˆ)m .

OR A truck and a car moving with the same kinetic energies (KE) on a straight road. Their engines are simultaneously switched off which on will stop at a lesser distance ? 9. Show that the function of time y = (sin wt – cos wt) represents simple harmonic motion.

10. Two springs of force constants K and 2K are connected to a block of m as shown below. what is the frequency of oscillation of this block?

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11. A cyclist is riding with a speed of 27km/h as he approaches a circular turn (on the road) of radius 80m, he applies brakes and reduces his speed at the constant rate 0.50 m/s2. Find the magnitude and direction of the net acceleration of the cyclist on circular turn ? 12. A cricketer can throw a ball to a maximum horizontal distance of 100 m. How much high above the ground can the cricketer throw the same ball.

13. The period of oscillation of a simple pendulum is T = 2π √𝑙

𝑔 measured

value of l is 20.0 cm known to 1mm accuracy and time for 100 oscillations of the pendulum is found to be 90s using a wrist watch of 1s resolution. What is the accuracy in determination of g? 14. Define the following: (a) Astronomical unit and Parsec (b) Average speed and average velocity (c) Dimension of a physical quantity. 15. State parallel axes theorem. Apply this theorem to find the moment of inertia of a solid sphere about the tangent of its surface.

16. Define escape speed. Show that its value on the surface is ve= √2𝑔𝑅.

R → radius of planet (Earth) 17. For two different type of rubber stress – strain curves are shown:

(a) To make a shock absorber which rubber will you prefer and why ? (b) To make car tyre which of the two rubber would you prefer and why ? 18. Two exactly similar rain drops felling with terminal velocity of (2)1/3 ms–1 coalesce to form a bigger drop. Find the terminal velocity of the bigger drop. 19. What is the effect of pressure on melting point of a substance? What is the regelation. Give its one practical application.

20. You have the following group of particles, ni represents no. of molecules with speed vi (ms–1):

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ni 2 4 8 6 3

vi 1.0 2.0 3.0 4.0 5.0

Calculate

(a) the average speed (b) the r.m.s. speed (c) the most probable speed 21. Explain why?

(a) inspite of the formula v = √𝛾𝑃

𝜌 the speed of sound in air independent of

pressure where γ → ratio of specific heats i.e., Cp /Cν , ρ →density, P →

pressure. (b) bats can ascertain distances, directions, nature and the size of the obstacles without any “eyes”. 22. Differentiate the following : (a) wave velocity and particle velocity, (b) harmonics and overtones

OR (a) What is beat phenomenon ? (b) A whistle revolve in a circle with angular velocity of w = 20 rad s–1. If the

frequency of the sound is 385 Hz and speed is 340 ms–1 than find the

frequency heard by the observer when the whistle is at B.

23. One day Ajit was having morning with his grand father. Then a cyclist took sharp turn on a plane curved road and fall down. Ajit helped him in getting up and asked him to keep the speed slow at sharp turn, the grandfather asked Ajit why every vehicle at sharp turn slows down Ajit explained this reason to his grandfather logically. (a) Which values are displayed by Ajit and his grandfather. (b) What is the maximum speed of cylist on a sharp turn of a plane road (circular) so that he would not turnover if the radius of the circular road is 3m and cofficient of friction between road and the type is 0.1.

Section - E 24. (a) What is an adiabatic process ? Derive expression for the work done during such process.

(b) A refrigerator is to maintain eatable kept inside at 9°C. If the room temperature is 36°C calculate the co-efficient of performance.

OR

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State first law of thermodynamics. On the basis of this establish the relation between two molar specific heats for an ideal gas. 25. Prove that the velocity v of translation of a rolling body (like a ring, disc, cylinder or sphere) at the bottom of an inclined plane of height h is given by :

Note K is the radius of gyration of the body about its symmetry axis, and R is the radius of the body. The body starts from rest at the top of the plane.

OR A 1 kg block situated on a rough incline is connected to a spring of spring constant 100 Nm–1 as shown below. The block is release from rest with the spring in the unstretched position. The block moves 10cm down the incline before coming to rest. Find the coefficient of friction between the block and the incline. Assume that the spring has a negligible mass and the pulley is frictionless. k = 100 Nm-1

26. State parallelogram law of vector addition and Find the magnitude and direction of resultant of two vectors A and B in terms of their magnitude and angle between them.

OR The speed time graph of a particle moving along a fixed direction is shown below. Obtain the distance traversed by the particle between (a) t = 0s to 5s, (b) t = 2s to 6s

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SOLUTION OF MODEL QUESTION PAPER

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Q13

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Diagram 1

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19. The melting of those substances which expand on melting, increase with increase in pressure while the melting point of those substances which contract on melting, decrease with increase in pressure. The phenomenon in which ice melts when pressure is increased and again freezes when pressure is removed is called Regelation. Practical examples.

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