AQA GCSE Forces and Elasticity

Forces and Elasticity

Definition of a force: A force is a push or pull that acts on an object due to the interaction with another object.

Forces can change the shape of an object by:

1.Compression of object

2.Bending of object

3.Stretching of object

Compression

Objects can be squashed when a compression force acts on the object.

A compression force acts downwards on the can. In response the table exerts an upwards reaction force that is the same size as the compression force, but in the opposite direction on the can.

As a result the can is crushed.

There are other forces involved in this example, but they have been removed for simplicity.

Stretching

In the case of a man pulling on a rope. He will exert an applied pull force on the rope. In response the rope will have a tension force which acts in the opposite direction.

Bending

A spoon can be bent by applying forces to the spoon.

The spoon is bent by applying two downward forces to the ends of the spoon, whilst applying an upward force to the spoon.

Inelastic and Elastic Deformation.

Deformation is when an object changes its shape.

There are two types of deformation:

1.Inelastic deformation

2.Elastic deformation.

Inelastic deformation

When a stretching force is applied to an object it will be deformed (change shape).

When the stretching force is removed, if the object does not return to its original length and shape, then inelastic deformation has occurred.

Due to the stretching forces, the metal chain has been permanently deformed and when those pulling forces are removed the chain will not return to its original length and shape, so inelastic deformation occurs.

Elastic deformation

When a stretching force is applied, the object will be deformed. However, when that stretching force is removed the object will return to its original length and shape.

An example is a rubber bungee cord. During the person’s downward fall, the bungee cord stretches, but then recoils.