Pressure

Pressure is how much force is put on a certain area. It is measured in pascals. You can calculate the pressure by doing:

Force (N) / Area (M)= Pressure (Pa)

The larger the surface area, the smaller the pressure. If you have a screw with a pointy end, then it is easier to drill as all the pressure can be focused onto one point.

Atmosphereic pressure is all around us. It is constantly pushing down on us, but we are used to it and do not feel it. The lower you are, the more atmosphere above you and therefore the bigger the atmospheric pressure. So if you are on top of a mountain, the atmospheric pressure will be less.

Pressure in water increases with depth as more water pushes down above you. So if you swam to the bottom of the atlantic, you would be compressed by all of the pressure pushing down on you. Because water pressure increases with depth, the force pushing upwards at the botom of the object is greater than the force pushing down at the top. The force pushing up is called upthrust. If the upthrust equals the force oushing down (gravity) then the object will float. If not, it will sink.