The goal of physics is to provide an understanding of nature. The science of physics was developed to explain our physical environment.
Pushes or Pulls are very general names given to forces. A physicist is much more precise when describing forces acting on a body using terms like weight, frictional force, tension, normal reaction force, electrical force, magnetic force etc.
The pressure exerted by a liquid on the base of the container depends on the vertical height of the liquid over it not on the area of cross-section. As one goes deeper in the swimming pool, the pressure on the ear drum is found to increase.
The word force in common usage refers to a push or pull. The word Mass is also just as familiar as the word force. A super tanker is one that contains an enormous amount of mass. In comparison a coin does not contain much mass.
We have learnt that a force changes or tends to change the state of rest, speed or direction of motion of an object, i.e., the force produces an acceleration. In this chapter, we are going to identify one of the forces which produces acceleration in all objects on the surface of the Earth irrespective of their mass.
For a layman the term 'work' implies any activity resulting in muscular or mental exertion. In physics, however, the term has a different meaning. It represents a physical quantity.
From times immemorial, man has used machines to help him in his work. Today, we are dependent on machine for almost every task. When we think of machines we always tend to think of big and complicated units with many moving parts like wheels and rollers and gears and shafts. In Physics the term 'machine' has a specific meaning.
Static electricity was known to people more than 2500 years ago. The Greeks knew about the attractive property of the resin amber. They knew that by rubbing amber with cloth, it could be made to attract small feathers. The Greek name for amber was 'elektron'.
It is believed that around 2000 BC the Chinese had already discovered the magnetic property of natural iron ore. In a part of Turkey formerly called Magnesia, there are deposits of an iron one which has the property of attracting iron. As this ore was discovered by Greeks they called it magnetite. This natural magnet was used by mariners for navigation and was called "Lodestone".
Take two beakers one with hot water and another with cold water. Dip your fingers in hot water your finger experience hotness. Then dip your fingers in cold water. Your fingers experience coldness.
Today the fact that all matter is made up of atoms is universally accepted. Realisation of the atomic constituents of matter began in 1828 when Scottish botanist Robert Brown observed a random ceaseless motion of pollen grains suspended in a liquid. Many macroscopic properties and phenomena observed can be explained using this microscopic picture of matter being composed of atoms or molecules possessing some form of motion.
In the previous chapters we studied the different types of motion like uniform motion, accelerated motion, projectile motion and periodic motion. We then learnt to relate the acceleration of the body to the force applied. In this chapter we shall study the motion of collection of particles - wave motion.