# IFS (Forests Services) Physics (Mains): Questions 13 - 17 of 34

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## Question number: 13

» Special Relativity, Waves & Geometrical Optics » Waves » Damped Oscillation

Appeared in Year: 2013

### Write in Short

A block of mass is attached to one end of a combination of two massless springs connected in series. The other end of the combination is fixed to a rigid support. The spring constatnts of the two springs are and , respectively. The block is free to move on a frictionless horizontal surface. If the block is pulled a little and then released, calculate the frequency of oscillation of the block. (Section A)

## Question number: 14

» Thermal and Statistical Physics » Statistical Physics » Bose-Einstein Condensation

Appeared in Year: 2012

### Describe in Detail

What are Einstein’s A and B coefficients? Establish a relation between the. (Section A)

### Explanation

There are three Einstein coefficients associated with any pair of energy levels. Of these three only one is independent. The other two dependent upon the coefficient taken to be independent, plus the frequency of the transition and the statistical weight of the two associated terms.

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## Question number: 15

» Classical Mechanics » Particle Dynamics » Conservation of Linear and Angular Momentum

Appeared in Year: 2010

### Describe in Detail

Establish the relation between the angular momentum and torque of a particle. Show that this relation leads one to the principle of conservation of angular momentum. (Section A)

### Explanation

Angular momentum is a measure of body is given by the cross product of linear momentum and position vector from the axis of rotation.

Where, is distance from the axis of rotation and the is the linear momentum of the body.

Torque is defined as a moment of force or tendency of a force to rotate an object about an axis. Which is represent

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## Question number: 16

» Special Relativity, Waves & Geometrical Optics » Geometrical Optics » System of Two Thin Lenses

Appeared in Year: 2010

### Describe in Detail

Consider a system of two thin lenses of focal lengths and separated by a distance of in air. For an object of height placed at a distance of in front of the convex lens, find the size and position of the image. (Section A)

### Explanation

Image from first lens is given as,

- Now, the distance between lenses is , therefore for second lens image of first lens becomes object of second lens;

- So, for second lens,

- The image of object is at far from the second lens.
- Now, magnifica

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## Question number: 17

» Classical Mechanics » System of Particles » Constraints

Appeared in Year: 2010

### Describe in Detail

How can one introduce the constraints of motion through the concept of generalized coordinate systems? Write down the set of transformation equations for a system of particles relating the generalized coordinates with real coordinates. (Section A)

### Explanation

In mechanics, mostly problems can be reduced by solving differential equation, which consist of all the forces acting on a system. A such equation is given by,

As we know, all mechanical systems have constraint force acting on them to some degree. A constrain in which the equations connecting the coordinates of the particles

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