Physics

Sound is a form of energy produced by a vibrating body, which requires medium to travel. Sound travels in the form of waves. The audible sound has frequency range 20 Hz to 20 kHz.

The motion that repeats itself after regular intervals of time is called periodic motion. If a particle in the periodic motion moves to and fro over the same path, the motion is said to be vibrating or oscillating.

Thermodynamics is the subject dealing with quantitative relation between heat energy and other forms of energy in physico-chemical processes. These results are formulated in to four laws - zero, first, second and third laws of thermodynamics.

In general heat travels from one point to another whenever there is a difference of temperatures. Heat flows from a body at higher temperature to a lower temperature. Heat is transferred or propagated by three distinct processes - conduction, convection and radiation.

The temperature of a body is a state which determines the direction of flow of heat or the degree of hotness of a body. Heat is the cause and temperature is the effect.

The properties of a surface are quite different from the properties of the bulk material. A molecule well inside a body is surrounded by similar particles from all sides. But a molecule on the surface has particles of one type on one side and of different type on the other side.

A substance which can flow is known as fluid. Hence, the term includes both liquids and gases. The study of fluids at rest is called fluid statics.

The external force acting on a body on account of which its size or shape or both change is defined as the deforming force. The force which restores the size and shape of the body when deformation forces are removed is called restoring force.

Newton’s Law of Universal Gravitation: Every two bodies in the universe attract each other with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

Every particle is attracted towards the centre of the earth by the force of gravity and the centre of gravity of a body is the point where the resultant force of attraction of the weight of the body acts.

Collision is an interaction between two or more bodies in which sudden changes of momentum take place. For example, striking a ball with a bat.

The product of force and displacement (in the direction of force), during which the force is acting, is defined as work.

When a body is in motion over another surface or when an object moves through a viscous medium like air or water or when a body rolls over another, there is a resistance to the motion because of the interaction of the object with its surroundings. Such a resistance force is called force of friction.

The branch of Physics that deals with the motion of a body due to the application of force is called mechanics. Mechanics is divided into two branches namely dynamics and statics.

Every measurement has two parts. The first is a number (n) and the next is a unit (u). Q = nu. For example, Length of an object = 35 cm. The number expressing the magnitude of a physical quantity is inversely proportional to the unit selected.