Subject : Physics - 2012 Theory

Time: 3 Hrs

Class: XI

M.M.: 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 questions 28 to 30 carry five marks each.

З. There is no overall choice. However an internal choice has been provided in one question of 2 marks, one question of 3 marks and all of the three questions of 5 marks each. You have to attempt only one of the choices in such questions.

Use of calculator is not permitted.

1. Write the dimensional formula for angular momentum.
2. Two bodies of masses m, and m, have equal momentum. Show which one has greater kinetic energy? Given <math>m_1 > m_2</math>.
3. State perpendicular axis theorem for a plane lamina.
4. State first law of themodynamics.
5. Two vessels of equal capacity have gases at the same temperature and pressure. The first vessel contains neon (monoatomic) the second contains chlorine (diatomic) gas. Which one has greater root mean squared speed.
6. Define coefficent of thermal conductivity.
7. Two sound sources produce 12 beats in 4 seconds. By how much do their frequencies differ?
8. What is resonance phenomenon?
9. The escape speed V of a body depends upon
10. acceleration due to gravity 'g' of the planet
11. the radius of the planet R.

Establish dimensionally the relationship in V, g and R.

Aplayer throws a ball upwards with an initial speed u m/s.

1. What is the direction of acceleration during the upward motion of the ball?
2. What is the direction of velocity during the upward motion?
3. What are the velocity and acceleration of the ball at the highest point of its motion?

A body of mass 0.25 kg moving with velocity 12 m/s is stopped by applying a force of 0.6N. Calculate the time taken to stop the body.

XI - Physics 227

Two bodies A and B of masses 10kg and 20kg respectively kept on a smooth, horizontal surface are tied to the ends of a light string. A horizontal force F = 600 N is applied to A. What is the tension on the string?

F ← A В

Two equal forces have their resultant equal to either. What is the inclination between them.

An elastic spring of spring constant k is compressed by an amount x. Obtain an expression for its potential energy.

State parallel axis theorem. What is the moment of incertia of a ring about an axis perpendicular to its plane and tangent to the ring.

<math>M \rightarrow \text{mass of ring}, r \rightarrow \text{radius}.</math>

According to Newton's law of gravitation, the apple and the earth experience equal and opposite forces due to gravitation. But it is the apple that falls towards the earth and not vice versa. Why?

1. Draw energy distribution curve for a black body at two different temperatures T, and T, (T,>T,). Write two conclusion that can be drawn from these curves.

Define mean free path of molecules in a gas. Obtain an expression for it.

1. Molar volume is the volume occupied by one mole of an ideal gas at standard temperature and pressure. Show that it is 22.4 litres. (S.T.P.: Pressure = 1 atmosphere, Temperature = 0°C)

A particle starts from origin at t = 0 with a velocity 5.0 i m/s and moves in xy plane under the action of a force which produces a constant acceleration of <math>(3.0 i + 2.0 j) \text{ ms}^{-2}</math>

1. What is the y – coordinate of the particles and the instant its x – coordinate is 84m?
2. What is the speed of the particle at this time?

Obtain an expression for maximum speed of a vehicle which can be achieved while taking a turn on a banked circular road.

Define the term "Coefficient of limiting friction between two surface." A body of mass 10kg is placed on an inclined surface at an angle of 30°. If the coefficient of limiting friction is <math>\frac{1}{\sqrt{3}}</math>, find the force required to just push the body up the inclined surface. The force is being applied parallel to the inclined surface.

Find the scalar and vector products of two vectors.

<math>\vec{A} = 3\hat{i} - 4\hat{j} + 5\hat{k}</math> and <math>\vec{B} = -2\hat{i} + \hat{j} - 3\hat{k}</math>

Obtain an expression for kinetic energy of rotation of a body with angular velocity 'ω' and hence define moment of inertia.

XI - Physics 228