## Archimedes’ Principle

When a stone is immersed in a bucket completely filled with water, some amount of water spill out of the bucket. The weight of water displaced (spilled) from the bucket can be explained by Archimedes principle.

When a stone is immersed in a bucket completely filled with water, some amount of water spill out of the bucket. The weight of water displaced (spilled) from the bucket can be explained by Archimedes principle.

Bragg’s law was first proposed by Sir William Bragg and his son Sir Lawrence Bragg. They studied about the diffraction of X-rays and devised a method for determining the wavelength of X-rays.

When an object is thrown vertically upwards, it reaches a certain height and comes back to the earth. But when it is given greater initial velocity, it reaches greater height before coming back.

The center of gravity (not to be confused with center of mass) of a body is a point where the weight of the body acts and total gravitational torque on the body is zero.

The center of mass (not to be confused with center to gravity) of a body is the point which behaves as if all the mass of the body is concentrated there. Thus, if a force acts at this point, the body will accelerate but will not rotate.

The moment of linear momentum of an object is called angular momentum. Angular momentum is represented by L. The angular momentum of an object about an axis of rotation is measured by the product of the linear momentum of the object and the perpendicular distance between the object and the axis of rotation.

Radius of gyration is defined as the distance from the axis of rotation to a point where the total mass of the body is supposed to be concentrated, so that the moment of inertia about the axis may remain the same. Simply, gyration is the distribution of the components of an object. It is denoted by K.

According to Newton, when sound waves propagate in air, compression and rarefaction are formed. He assumed that the process is very slow and the heat produced during compression is given to surrounding and heat loss during compression is gained from surrounding. So the temperature remains constant and sound waves propagate through an isothermal process.

Michelsons’s Method is a precise method for measuring the speed of light. An octagonal mirror M1 is mounted on the shaft of a variable speed motor. Light from a bright source S is focused at an angle of 45o on one of the faces of mirror M1 after passing through a slit S1. The reflected light falls on a distant concave mirror M2.

According to law of conservation of energy, Energy of an isolated system is constant. It can neither be created nor be destroyed but it can be transformed from one type to another. For example, when an object falls on the ground from a certain height, its kinetic energy is converted into other forms of energy such as sound energy, heat energy, light energy, etc.