Deforming Forces

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This is a basic physics tutorial that is targeted at GCSE (grade 9 and grade 10) standard reviewing deformation forces. The video for this written tutorial is on its way.

What is Deformation?

Deformation is what occurs when a force changes the shape of an object, rather than moving it. This change can be really obvious. For example, it's easy to see how play-doh changes shape when you squeeze it between your fingers (mouse over the image below).

At other times, the deformation is so subtle it's hard to tell it's happened. For example, a sky-scraper building can sway up to almost a metre because of forces pushing on it by the wind.

Deformation can only occur with more than one force

If only one force is applied to an object, it will not deform. Instead, it will move in the direction of the exerted force.

But when more than one force is exerted, and in different directions, deformation will occur. This is illustrated below with three different deforming forces: tension, compression and bending. (Hint: roll your mouse over the image to these forces illustrated)

Tension is when the forces cause stretching of the object. Compression is when the forces cause shortening. Bending is as the name suggests - the forces cause the object to bend.

Anchoring Objects

An alternative to specifically exerting two forces on an object is to anchor one side. When a force is exerted on the free end, the anchored side exerts a force on the anchor which in return exerts an equal and opposite reaction force on the object.

The action force exerted by the hand results in a reaction force being exerted on the anchored end.

Reversible and Irreversible Deformation

Some materials will deform reversibly; that is, the material will go back to its original shape once you remove the forces. This type of deformation is called elastic deformation. The skyscraper undergoes elastic deformation; once the wind settles down, the elements of the building return to their original position.

Some materials will deform irreversibly; that is, the material's shape will be permanently changed, and it will not revert back to its original shape when you remove the forces. This can be referred to as permanent deformation. The play-doh undergoes irreversible deformation; it will not revert back to its original shape by itself when the forces have been removed.

Whether an object undergoes permanent or reversible deformation is a property of the material. If it undergoes reversible elastic deformation, there can be variations in the extent to which this occurs. We'll learn more about that in the next tutorial.