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# Physics, XI

Try out this sample question and answer it in your H.W. book.

Date of submission: 03-11-15

KENDRIYA VIDYALAYA, PATTOM

HALF YEARLY SAMPLE QUESTION

CLASS XI PHYSICS Max. marks:70

General Instructions:-

i. All questions are compulsory.

ii. There are 23 questions. Qns.1-5 carry 1 mark each, Qns.6-10 carry 2 marks each, Qns.11-22 carry 3 marks each, Qns.24-26 carry 5 marks each.

iii. Qns.23 is a value based question and carry 4 marks.

iv. Overall choice is not allowed. However, internal choices are provided. You are to attempt only one of the choices in such questions.

v. You may use the following physical quantities wherever required.

c= 3 x 108m/s.

Planck’s constant, h= 6.626 x 10-34 Js.

Boltzmann constant k= 1.381 x 10-23 J/K.

Avogadro’s number NA = 6.022 x 10 23 mole-1.

Mass of earth = 6 x 1024 Kg.

1) What is the numerical ratio of velocity to speed of an object?

2) Can a body have constant speed and still have a varying velocity? Explain:-

3) Why a pilot looping a vertical loop not fall down even at the highest point?

4) Why is it more difficult to revolve a stone tied to a larger string than a stone tied to a smaller string?

5) The velocity of a moving particle is given by V = 6 + 18t + 9t2 where x is in meters and t is in seconds. What is its acceleration at t=2 s?

6)

 Q

 Q
 A
 Q
 x

The escape velocity V of a body depends upon ( i ) the acceleration due to gravity of the planet (g) (ii) the radius of the planet (R). Dimensionally establish a relationship between V, g and R.

7) The graph gives the position- time (x-t) graphs

 P

for two children A and B returning from school

 A
 A

O to their homes P and Q respectively. Now,

 B
 t

(a) Who lives closer, A or B?

(b) Who started earlier from school, A or B?

(c) Who walked faster, A or B?

(d) Who reached home earlier, A or B?

8) State and prove Polygon law of vector addition:-

9) Define angle of friction. Show how it is related with coefficient of static

friction:- OR

Define angle of repose. Show how it is related with angle of friction?

10) A light body and a heavy body have the same kinetic energy. Which one

11) The shadow of a tower standing on a level plane is found to be 50m

longer when sun’s altitude is 300 than when it is at 600. Find the height of the tower.

h

12) Derive graphically the following equations of motion for a uniformly

accelerated motion:-

(a) s= ut + ½ at2

(b) v2-u2 = 2as

13) Define relative velocity . Deduce an expression for relative velocity of an

object with respect to another in terms of their velocities relative to

earth. Hence, draw position-time graphs of two objects moving along a

straight line, when their relative velocity is:-

(i) +ve, (ii) -ve (iii) zero

14) If = 3 + 2 and If = – 2 +3 , find the magnitude of ( + ) and

(.

OR

Find the angle between the vectors = + 2 and =- + -2 .

15) Consider a body of mass m tied to one end of a string and rotating in a

vertical circle of radius r. Show that the minimum velocity of projection

at the lowest point for looping the loop is v = .

16) Prove the work- energy theorem for a variable force.

17) What will be the duration of a day, if earth suddenly shrinks to of

its original volume, mass remaining the same?[M.I of solid sphere = MR2 ]

18) Derive an expression for moment of inertia of a ring about a tangent in

its own plane. Given, moment of inertia of a ring about an axis through

its centre and perpendicular to its plane = MR2/2.

19) State the principle of conservation of angular momentum. Give any two

practical applications.

20) Define escape velocity. Derive an expression for escape velocity of a

body from the surface of earth.

21) Moon has no atmosphere. Why?

22) What are conservative and non- conservative forces? Give examples.

23) One rainy day, Devu was returning back home from school with her

elder sister Malu. On the way back home, they saw a running boy skidding and falling. Both the girls helped the boy to get up. Then, Devu asked her sister why after a rain we skid and fall.

(a) What might be the reason Malu has given to Devu?

(b) Give two values exhibited by the girls.

24) Define projectile. Show that its path is parabolic. Also, find expressions

for (i) maximum height attained and (ii) time of flight.

OR

Define centripetal force. Derive an expression for the centripetal

acceleration of a body moving with uniform speed v along a circular path

of radius r. show that it acts along the radius towards the centre of the

circular path.

25) State the law of conservation of mechanical energy. Show that the total

mechanical energy of a body falling freely under gravity is conserved.

Show it graphically.

OR

Define elastic collision. Prove that the relative velocity of approach

before collision is equal to relative velocity of separation after collision.

Hence, derive expressions for velocities of two bodies after collision

in terms of their initial velocities before collision.

26) Obtain an expression for acceleration due to gravity on the surface of

earth. Discuss its variation with altitude, depth and shape of earth.

OR

Define orbital velocity and time period of a satellite. Derive expressions

for these.

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