EXAMINATION PAPER: 2011

Time: 3 hours

Maximum Marks: 70

General Instructions:

1. All questions are compulsory.
2. There are 30 questions in total. Questions 1 to 8 carry one mark each, questions 9 to 18 carry two marks each, questions 19 to 27 carry three marks each and question 28 to 30 carry five marks each.

1. There is no overall choice. However, an internal choice has been provided in the one question of two marks; one question of three marks and all three questions of five marks each. You have to attempt only one of the choices in such questions.

1. Use of calculators is not permitted.
2. Please write down the serial number of question before attempting it.
3. You may use the following values of physical constants wherever necessary. Boltzmann's constant K = 1.38 x 10^-23 JK^-1

Avogadro's number N_A = 6.022 × 10²³/mol

Radius of Earth <math>R_e = 6400</math> km. <math>= 1.013 \times 10^5 \text{ Pa}</math>

1 Atmospheric Pressure g = 9.8 m/s²

<math>R = 8.3 \text{ J mol}^{-1} \text{ K}^{-1}</math> 1 Write the dimensional formula of torque.

Draw velocity-time graph for an object, starting from rest. Acceleration is constant and remains positive. 1

Arrange increasing order the tension T₁, T₂ and T₃ in the figure.

<math>T_1</math> <math>T_2</math> <math>T_3</math> <math>T_4</math> <math>T_5</math> <math>T_7</math>

1. Why there is lack of atmosphere on the surface of moon?
2. The triple point of carbon dioxide is 216.55 K. Express this temperature on Fahrenheit scale.
3. Physics

203

1. In an open organ pipe, third harmonic is 450 Hz. What is the frequency of fifth harmonic?
2. Which type of substances are called elastomers? Give one example 1

A simple harmonic motion is described by a = -16 x where a is acceleration, x → displacement in m. What is the time period? 1

1. Percentage error in the measurement of height and radius of cylinder are x and y respectively. Find percentage error in the measurement of volume. Which of the two measurements height or radius need more attention? 2

OR

The length and breadth of a rectangle are measured as <math>(a \pm \Delta a)</math> and <math>(b \pm \Delta a)</math> Δb) respectively. Find (i) relative error. (ii) absolute error in the measurement of area. 2

1. An object moving on a straight line covers first half of the distance at speed v and second half of the distance at speed 2v. Find (i) average speed, (ii) mean speed.
2. An object moving on a circular path in horizontal plane. Radius of the paths is r and constant speed is v. Deduce expression for centripetal acceleration. 2
3. Find the height from the surface of earth at which weight of a body of mass m will be reduced by 36% of its weight on the surface. (R_a = 6400 km) 2

Define gravitational potential. Give its S.I. unit.

An engine has been designed to work between source and sink at temperature 177°C and 27°C respectively. If energy input is 3600 J. What is the work done by the engine? 2

Explain :

1. Why does the air pressure in a car tyre during driving increase?
2. Why coolant used in a chemical plant should have high specific heat? 2

Calculate the work done in blowing a soap bubble from a radius of 2 cm to 3 cm. The surface tension of the soap solution is 30 dynes cm-1. 2

XI - Physics 204