Science Projects Index

For Every Action There is an Equal and Opposite Reaction

This is Newton's famous third law of motion. It is very easy to demonstrate this principle. Blow up a balloon and then leave it, so that the air escapes. You will see the balloon is shooting into the direction opposite to that of the neck of the balloon, through which the air is escaping. This is the principle used in jet planes and rockets.

Bearings and Their Effects

You must have seen ball bearings inside your cycle wheel hub.

They reduce the friction inside the hub when the cycle is in motion. You can understand how this happens with a simple experiment. Keep a small wooden plank on another bigger wooden plank. Slowly raise the lower plank and see if the smaller plank on the top is sliding down. You will see that the movement is very slow, as there is friction between the planks and hence resistance on motion. Now place four pencils between the planks, so that the smaller plank is on it. Raise the lower plank. What do you find?