KENDRIYA VIDYALYA SANGATHAN CHANDIGARH REGION

SESSION ENDING EXAMINATION SESSION-2017-18

SUBJECT: PHYSICS

Time: 3 hrs. Class- XI M.M.-70

General Instructions:

1)All questions are compulsory.

2)There is no overall choice. However an internal choice has been provided in one question of two marks, one question of three marks and in all three questions of 5 marks.

3)Questions 1 to 5 are very short answer questions carrying 1mark each.

4)Questions 6 to 10 are short answer questions carrying 2 marks each.

5)Questions 11 to 22 are also short answer questions carrying 3 marks each.

6)Question 23 is value based question carrying 4 marks.

7)Questions 24 to 26 are long answer questions carrying 5 marks each

SECTION A

1. If.= ,find the value of angle between and. 1

2. Can a body have zero velocity and still be accelerating? Explain? 1

3. Explain with reason whether the potential energy in the following cases increase or

decreases (a) a spring is compressed (b) a spring is stretched.1

4.Define radius of Gyration. `1

5. What are the two basic properties of a medium for propagation of waves?1

SECTION B

6. State parallel axis theorem on moment of inertia. What is the moment of inertia of a uniform rod of length ‘L’ and mass ‘m’ about an axis perpendicular to it through one end? Given the moment of inertia about the centre of mass is ML2. 2

7. Derive an expression for orbital velocity of a satellite.

OR

Derive an expression for escape velocity of a body from the surface of earth. 2

8. Discuss the kinetic interpretation of temperature. Hence define absolute zero. 2

9. State Zeroth law of Thermodynamics. How does it lead to the concept of temperature? 2

10. Draw stress versus strain curve for a loaded wire indicating permanent set, elastic limit, yield point, and fracture point. 2

SECTION C

11. Assuming that mass ‘m’ of largest stone that can be moved by a flowing river depends on the velocity ‘v’, the density ‘ρ’ of the water and acceleration due to gravity ‘g’. Show that mass ‘m’ varies as sixth power of the velocity of flow, using dimensional analysis? 3

12. Define relative velocity. A stone is thrown upward with velocity ‘v’ comes down after

time‘t’. Draw the graph showing the variation of speed with time and velocity with time

for its entire motion. 3

13. A batsman deflects a ball by an angle of 45o without changing its initial speed which is equal to 54 Km/hr. What is the impulse imparted to the ball? Mass of the ball is 0.15 Kg.

OR

A bomb at rest explodes into three fragments of equal masses. Two fragments fly off at right angles to each other with velocities 9m/s and 12m/s. Calculate the speed of the third fragment. 3

14. Define angle of friction and angle of repose. Derive a relation between them. 3

15. Define moment of inertia of a body. State two factors on which it depends. A ring and a circular disc of different materials have equal masses and equal radii. Which one will have a larger moment of inertia about an axis passing through its centre of mass perpendicular to its plane? 3

16. Define acceleration due to gravity.Derive an expression for the variation of ‘g’ with height from the surface of earth. 3

17. Explain surface energy. Establish its relation with surface tension? 3

18. A thermodynamic system is taken from an original state D to an intermediate state E by the linear process as shown in the figure. Its volume is then reduced to the original value from E to D via F by an isobaric process. Calculate the (i) Work done by the gas from D to E (ii) Work done on the gas from E to F (iii) Find the net work done from D to E to F. 3

19. What do you mean by degrees of freedom? Write degrees of freedom of a diatomic molecule. Hence find specific heat of one mole of diatomic gas at constant volume using law of equipartition of energy. 3

20. Show that the small oscillations the motion of a simple pendulum is simple harmonic. Derive the expression for its time period. Does it depend on mass of the bob?3

21. State Doppler Effect in sound. Derive the relation for the apparent frequency when the source is moving towards stationary observer in still medium. 3

22. What are standing waves? Write two differences between standing waves and progressive waves. 3

SECTION D

23. A monkey is sitting on a tree. Rahim seeing the Monkey brought some fruits and gave them to the Monkey, and ran into the house immediately. On hearing the sound produced when Rahim was running the monkey was scared and climbed the nearby tree.

(a) Write two values of Rahim which inspired you?

(b) A monkey of mass 40 Kg climbs on a rope which can stand a maximum tension of 600 N. In which of the following cases will the rope will break. The monkey

(i) Climbs up with an acceleration of 6 ms-2

(ii) Climbs down with an acceleration of 4 ms-2 4

SECTION E

24. State and prove Bernoulli’s theorem. It is advised not to stand near a running train. Why?

OR

Define capillarity. Derive ascent formula for rise of liquid in a capillary tube. Water rises in a capillary tube but mercury falls in the same tube. Why? 5

25. a) A body is projected at an angle θ with the horizontal. Obtain expressions for

its maximum height, time of flight and horizontal range.

b) A body is projected so that it has maximum range R. What is the maximum height reached during the flight?

OR

a) State the parallelogram law of vector addition. Show that resultant of two

Vector and inclined at angle θ is given by

R=

b) Two equal forces act at a point. The square of their resultant is 3 times of their

Product of two vectors. What is the angle between them? 5

26. (i)Prove that in one dimensional elastic collision between two bodies, the relative velocity of approach before collision is equal to the relative velocity of separation after collision. Hence derive expressions for velocities of two bodies in terms of their initial velocities before collision.

(ii)Hydrogenic materials are used as moderators in nuclear reactors to slow down the neutrons. Why?

OR

(i) State law of conservation of energy and show that the total mechanical energy of a

freely falling body remains constant throughout its fall.

(ii) A truck and car are moving with the same kinetic energy on a straight road. Their

engines are simultaneously switched off. Which one will stop at a lesser distance?5

End of the paper

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