EASY READ Science
What is pressure?
Pressure is the force exerted by something over a certain area. A nail goes into wood easily because the force hammering it in is concentrated on to the tiny area of the nail's sharp point. This produces high pressure. The same hammer blow might not make a blunt nail enter the wood because the force is spread out over a larger area: the blunt tip of the nail. Because of this, the pressure is lower.
Spreading weight
A jacana, a bird with long toes and claws, can walk over lilypads resting on the water's surface without sinking in. This because its weight is spread over a wide area, so its pressure is low.
Air pressure
Air feels weightless, but it contains gas molecules so it does have weight. In fact, the air above you is pressing down on you with the weight of a small car. You don’t feel it, because this pressure is balanced by the air pressing on you from every other direction, too—the pressure is equal on all parts of your body. Also, your body is not crushed because there is equal pressure inside and outside of it.
Air pressure decreases the higher up you go, because there are fewer and fewer gas molecules, so its weight becomes less and less.
Water pressure
The deeper you go in the water, the greater the pressure. Unprotected people cannot dive deeper than about 120 metres (400 feet) because the water pressure would crush them. Out of the water, the pressure of the air is balanced by the pressure of the liquids and gases inside your body.
Consultant: Mike Goldsmith
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