A sharp knife cuts easily, but a blunt knife does not. A ship made of iron floats, and a small iron nail sinks. We learn about pressure in solids, liquids and air, and about the upward push of a liquid. Then we meet the idea of Archimedes.
3 lessons, about 1 h 10 min3 simulations11 problems6 practice questionsPython in every lesson
Pressure is the thrust on each unit of area. The same force gives a big pressure on a small area and a small pressure on a big area.
A liquid pushes on its bottom and its walls. The pressure grows with the depth. The air has pressure too, and we live at the bottom of it.
A liquid pushes up on an object in it. This buoyant force is equal to the weight of the liquid that the object pushes aside. It decides if the object floats or sinks.
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