Material Science and Technology for kids


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Tension is a force that stretches something.  Compression is a force that squeezes something together.


Materials are only useful if they can withstand forces.  Force flows through a material like water flows through a pipe.  When a force is exerted on a material it flows through the material until it reaches earth.  The earth pushes upward on the material with the same force, so that the material does not move.


Materials can be though of as being made up of network of atoms connected by springs.  When the material experiences a force, the atoms move out of their normal positions and the springs react.  In a tensile force, the atoms are pulled apart and the springs are stretched until they break, which is when the material fails.  In a compressive force, the atoms are pushed together and the springs squeeze together until they break, which is when the material fails.


Concrete is an example of a material that is strong in compression and weak in tension.  This is why it is useful in walls, such as brick walls, where all the forces from the bricks, the upper floors and the roof act as compressive forces on the concrete bricks.