To investigate the stretching of an elastic band when it has some load on it.

Saira Hamid                        Physics course work

11cm                                                Elastic Band

Investigation:

To investigate the stretching of an elastic band when it has some load on it.

Aim:

To find out how much load is needed for the elastic band to reach its elasticity limit.

Introduction:

By using an elastic band and some weights, I am going to find out how much weight in grams it takes the elastic band to reach its full elasticity limit before it snaps.

Background:

Hooke’s law of elasticity states that for relatively small deformations of an object the displacement or size of the deformation is directly proportional to the deforming force or load.

At relatively large values of applied force, the deformation of the elastic material is often larger than expected on the basis of Hooke’s law, even though the material remains its elasticity and returns to its original shape and size when the load is taken off.

Elasticity is the ability of a deformed material body to return to its original shape and size when the forces causing the elastic band to stretch are removed.  Most solids exhibit elastic behaviour.  This limit is called the elastic limit; this is when the elastic band has reached the maximum elasticity before it snaps.  If an elastic band has too many weights on it and has exceeded the limit it will snap.  The elastic limit depends on the type of solid used. E.g. a steel bar or wire can be extended elastically by only about 1% of its original length.  Where as rubber like materials such as elastic bands can have extensions of up to 1,000%.

The elastic limit is in principle different from the proportional limit, which marks the end of the elastic behaviour that can be described as Hooke’s law. Which is that  ‘The load is proportional to the displacement.’  The elastic limit nearly coincides with the proportional limit for some elastic materials.

Prediction:

I predict that the results graph for extension versus load is a straight line with a curve to it at the top when it has reached the elastic limit.  This shows that extension is directly proportional to the load. This is called Hooke’s law.

Preliminary Results:

I have planned to put a weight of up to 880g and to start of at the elastic bands original with a load of 0g.  So as part of my preliminary work I just want to check whether 880g is too much for the elastic band, ...