## Old Question Paper of Physics

Year: 2070 (2013) – Old is Gold

For: Science Grade XI

Subject Code: 110’D’ | Time: 3hrs | Full Marks: 75 | Pass Marks: 27

Candidates are required to give their answer in their own words as far as practicable. The figures in the margin indicate full marks.

## You may use the following values of physical constants wherever necessary.

Acceleration due to gravity (g) = 10 m/s^{2}

Specific heat capacity of copper = 400JKg^{-1}K^{-1}

Specific heat capacity of water = 4200JKg^{-1}K^{-1}

Latent heat of ice = 80 cal/gm

Young’s modulus of steel = 2 X 10^{11}Nm^{-2}

Permittivity of free space (E_{o}) = 8.854 X 10^{-12}C^{2}/Nm^{2}

## Group ‘A’

**1. Answer, in brief, any six questions: [6 X 2 = 12]**

a) The angle between two vectors and is θ. Find the magnitude and direction of X and .**.**

b) If y = a + bt + ct^{2}, where y is the distance and t is the time. What is the dimension and unit of c?

c) A projectile moves in a parabolic path without air resistance. Is there any point at which its acceleration is perpendicular to the velocity? Explain.

d) When a smooth-flowing stream of water comes out of a faucet, it narrows as it falls. Explain.

e) When four-legged animals walk, they always have three of their legs on the ground at any instant. Explain why?

f) Why is soap solution a better cleansing agent than ordinary water?

g) A fan with blades takes longer time to come to rest than without blades. Why?

**2. Answer, in brief, any two questions: [2 X 2 = 4]**

a) Does the cubical expansivity of a liquid depend on its original volume? Explain.

b) Animals curl into a ball, when they feel very cold. Why?

c) Define triple point and write its significance.

**3. Answer, in brief, any one questions: [2]**

a) What is illuminance? Name the factors upon which it depends.

b) Distinguish between real and virtual images.

**4. Answer, in brief, any one question: [2]**

a) More charge can be stored on a metal it it is highly polished than when its surface is rough. Explain.

b) What are the factors that determine the capacitance of a parallel plate capacitor?

## Group ‘B’

**5. Answer any three questions: [3 X 4 = 12]**

a) Define work. Derive an expression to calculate the work done by a variable force.

b) What is gravitational potential energy? Obtain an expression for the gravitational potential energy of a body at a distance r from the centre of the earth.

c) Define terminal velocity and hence describe the method of determining the coefficient of viscosity of a liquid using Stoke’s law.

d) Derive a relation between angular momentum and moment of inertia of a rigid body and hence define moment of inertia.

**6. Answer any two questions: [2 X 4 = 8]**

a) Define the coefficient of real and apparent expansion of a liquid and derive a relation between them.

b) What is a perfect gas? Prove that the average kinetic energy of a gas molecule is directly proportional to the absolute temperature of the gas.

c) Derive an expression for the work done during the adiabatic expansion of an ideal gas. Does the internal energy of the system change during adiabatic expansion?

**7. Answer any one questions: [4]**

a) What is lateral shift? Derive an expression for its value. How does the lateral shift change with the increase in the angle of incidence?

b) What is chromatic aberration? Show that for a lens, the chromatic aberration is the product of dispersive power and focal length of mean light.

**8. Answer any one questions: [4]**

a) What is electrostatic induction? How can you charge a boy positively by induction?

b) State and explain Gauss’s law in electrostatics. Use it to find the electric field intensity due a line charge.Group ‘C’

**9. Answer any three numerical questions: [3 X 4 = 12]**

a) In a physics lab experiment, a 6kg box is pushed across a flat table by a horizontal force F. if the box is moving at a constant speed of 0.35m/s and the coefficient of kinetic friction is 0.12, find the magnitude of force F. What is the magnitude of force F it the box is moving with a constant acceleration 0.18,/s^{2} ?

b) A certain string breaks when a weight of 25N acts on it. A mass of 500 gram is attached to one end of the string of 1m long and is rotated in a horizontal circle. Find the greatest number of revolution per minute which can be made without breaking the string.

c) Calculate the work done in stretching a steel wire 100cm in length end of cross sectional area 0.03cm2 when a load of 100 N is slowly applied without the elastic limit being reached.

d) A body is vibrating with simple harmonic motion of amplitude 15cm and frequency 4Hz. Calculate the maximum value of acceleration and velocity.

**10. Answer any two numerical questions: [2 X 4 = 8]**

a) A copper calorimeter of mass 300 gram contains 500 gram of water at 15°C. A 560 gram of aluminum ball at temperature of 100°C is dropped in the calorimeter and the temperature is increased to 25°C. Find the specific heat capacity of aluminum.

b) A metal rod of length 20cm and cross sectional area 3.14 cm^{2} is covered with non-conducting substance. One of its end it maintained at 100°C. while the other end is out in ice at 0°C. It is found that 25 gram of ice melts in 5 minutes. Calculate the thermal conductivity of the metal.

c) A petrol engine consumes 25kg of petrol per hour. The calorific value of petrol is 11.4 X 10^{6} cal/kg. The power of the engine is 99.75Kw. Calculate the efficiency of the engine.

**11. A refracting telescope has an objective of focal length 1m and an eye piece of focal length 2cm. A real image of the sun, 10cm in diameter, is formed on a screen 24 cm from the eye piece. What angle does the sun subtend at the objective? [4]**

**12. A parallel plate air capacitor of capacitance 245 X 10 ^{-12}F has a charge of magnitude 0.148µF on each plate. Find the potential difference and electric field intensity between the plates if the distance between plates is 5mm. [3]**