Physics has proved to be a subject of nature, as we have observed many scientists have been doing different research on basic phenomenas of life and nature. But today my presentation is little different. It is for something for young physicists to try out and enlighten their knowledge. Here is something for you to try out:
Open an umbrella, put it's end on the floor, open it and drop a ball into it. What do you observe? Now put a handkerchief into it, something unexpected will happen! The handkerchief will raw up the hedge and then flies off in a straight line.
This force which drives it out is called: "Centrifugal Force".
Is it possible to make a needle float on the surface of water like a straw? It seems impossible, it is a solid piece of steel and due to small area of contact,it forces almost zero upthrust,so it should sink. But no ,if you smear it with oil or fat and place it carrying on the surface of the water in a bowl it shall float! Surprising, why? The answer is: "Surface Tension".
Now something for your mom to try out! Do you know a fresh egg well sink in water, so if she wants to find out whether an egg is fresh,she tests it exactly in this way. If it floats it is not suitable for eating. A physicists infers from this observation that a fresh egg is heavier that the same volume of freshwater. Now if you prepare a strong solution of table salt then every fresh egg will float! Why? The answer to this is: "Upthrust".
Now let us try this. Cut a circle about the size of a glass hole from a postcard or a sheet of strong paper. Cut a spiral in it in form of a called up snake, make a small recess in the tail to receive a knitting pin joined upright. Now suspend it on top of an open lantern on a pot to a kettle. The snake will rotate! Why? Find your answer in "Convectional Flow of Air Current".
