Science Projects Index
Friction
Friction causes the slowing down of speed and heating. For example, if you rub two objects together, there will be heat produced due to friction.
This is the principle the ancient men used when they wanted to make fire. They used to rub two pieces of bamboo or rocks till sparks came out causing fire in nearby dry objects. And it is friction between the road and the tyre which causes the automobile to stop when braked.
When a parachute comes down, it is the friction between the air in the atmosphere and the parachute that it slows down the coming-down speed.