Deformation & Fluid Pressure
Explain forces associated with deforming objects (elastic and inelastic deformation), thermal expansion and contraction of materials, and how fluid pressure acts in all directions and increases with depth
What a learner can do afterwards
- Distinguishes elastic deformation (returns to shape) from inelastic/plastic deformation (permanently changed)
- Explains why bridges and railway tracks have expansion gaps
- Explains why pressure increases with depth in a liquid (e.g. why deep-sea divers need pressure suits)
- Gives an everyday example of thermal expansion causing a problem or being used usefully
The lesson
Push, pull, bend, or squeeze an object hard enough and you deform it: you change its shape. What happens once you stop pushing depends on how far you went.
Stretch a rubber band and let go. It snaps right back to its original shape. That is elastic deformation: the shape change undoes itself once the force is gone.
Now bend a paperclip a little. It springs back too, same as the rubber band. But bend it too far and it stays bent. Past a certain point the material cannot return to normal. That permanent change is called inelastic, or plastic, deformation.
Heat changes materials without any bending at all. Warming a solid makes its tiny particles vibrate more and push each other slightly farther apart, so the material expands. Cooling slows the particles down, and the material contracts. That is why bridges and railway tracks are built with small gaps: on a hot day the metal expands into the gap instead of buckling.
Materials can spring back (elastic) or stay changed (inelastic/plastic), heat makes materials expand while cold makes them contract, and fluid pressure pushes in every direction, growing stronger with depth.
Watch it
Where it sits
Learn first
This opens up
Nothing builds on it yet.
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.