 |
| Image created using Bing Image Creator |
You know those cartoons where Wile E. Coyote uses a giant magnet in one of his ill-fated plots to capture the Road Runner? It‘d be brilliant if such magnets exited, but unfortunately not. Gravity is one of the forces that act at long distances (well strictly gravity is not a proper force, but that's another story), however the force of a magnet is relatively localised to a region close to its north and south poles. So magnets in scrapyards can lift tons of metal, but they have to be lowered until they're nearly touching scrap. If the field strength of a magnet is increased sufficiently, the force can extend outwards some distance, but the force still obeys an inverse square law with respect to distance. So for instance let’s say the distance from a magnet is one cm. The force will have a certain value. At two cm, the force decreases to one quarter that value and at three cm to one ninth the value (nine being the square of three). At four cm, it’ll have fallen to one sixteenth the strength it was at one cm, and so on. To complicate things, force follows an inverse cube law close to a magnet, which causes an initial rapid drop-off in attractive force. Many parameters in nature follow an inverse square law, for example the brightness of an omnidirectional (the same in all directions) light source or the loudness of a sound source as an observer moves away from the source. Gravity also follows an inverse square law and the force of attraction between two bodies is proportional to the product of their masses (Either body being more massive increases the force) and inversely proportional to the square of their distance apart. (all of this discovered by Isaac Newton, the scientist and mathematician). The force of gravity of the Sun on a 70 kg person is about 42 g.