Planning

The aim of this experiment is to find out if the amount of weight applied to an elastic or stretchable object is proportional to the amount the object's length increases by when the weight is applied.

Since Hooke's law is famous, and is used a lot, I have many resources and researchable information available to use. I took this from a website;

http://www.efunda.com/formulae/solid_mechanics/mat_mechanics/hooke.cfm

"Robert Hooke, who in 1676 stated,

The power (Sic.) of any springy body is in the same proportion with the extension.

He announced the birth of elasticity. Hooke's statement expressed mathematically is,

[IMAGE]

where F is the applied force (and not the power, as Hooke mistakenly suggested), u is the deformation of the elastic body subjected to the force F, and k is the spring constant (i.e. the ratio of previous two parameters)."

The equation will be very useful in calculating the change in size, and for preparing my hypothesis. I took this from

http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0021767.html.

Elasticity (physics)

In physics, the ability of a solid to recover its shape once deforming forces (stresses modifying its dimensions or shape) are removed. An elastic material obeys Hooke's law, which states that its deformation is proportional to the applied stress up to a certain point, called the elastic limit, beyond which additional stress will deform it permanently. Elastic materials include metals and rubber. However, all materials have some degree of elasticity.

This was taken from the text book issued to me from my school:

" The extension is directly proportional to the load.

This is called Hooke's Law. This law also applies to the stretching of metal wires and bars.

From your results, plot a graph of extension against load.

[IMAGE]

A straight line through the origin of the graph confirms that the extension is directly proportional to the stretching force.

What happens with very heavy loads?

Hooke's Law only applies to the straight part of the graph (up to the limit of proportionality)."

The point P is called the elastic limit. If a spring is taken beyond this limit, it will not return to its old shape. It is permanently deformed.

Hooke's Law also applies to your bed-springs, to car springs, and to the steel girders used to bridges and buildings.

Graphs of extension; load are important to construction engineers."

I plan to take a wide range of results for this experiment, to ensure I get accurate readings and a good sense that Hooke's law works in a wide range of examples. Certain Results may have to be repeated due to the spring breaking, or if the spring is used too much, it may be permanently stretched out of shape, this will produce anomalous results.

Apparatus:

These are the equipment pieces id need to use:

• 30cm Ruler

• Spring with hooks at each end.

• Retort stand and clamp

• Varied Selection of weights

• Weight holder with hook at the end.

[IMAGE]

Method:

* Collect and set up apparatus as shown in diagram.

* Measure the spring's original length.

* Place required amount of weight on weight holder

* Measure the spring's new length.

* Record results in suitable table

* Remove weights and start experiment again with different amount of weights.

As a safety precaution I will ensure the spring is not stretched so much it could fly off and injure someone's eye.

Hypothesis:

I predict that I will find that the more weight that is added, the greater the extension of the spring will be. The change in weight will be proportional to the change in the length of the spring. I think this will happen because the greater the mass (measured in Kilograms, or Kg for short) an object has the greater the weight (measured in Newton's, or N for short) it will have....