# To investigate the behaviour ofan elastic material when a tensile force is applied.

## Sian Jones 11BGC

Aim: To investigate the behaviour of an elastic material when a tensile force is applied.

What I know: In the 1660s Robert Hooke investigated how springs and wires stretched when loads were applied. He found out that for many materials, the extension and load were in proportion provided the elastic limit was not exceeded.

Materials can be compressed as well as stretched. If a material is stretched but springs back to its original shape they are known as elastic. However they stop being elastic if bent or stretched too far. They either break or become permanently deformed.

The springs represent the bonds caused by the forces of attraction and repulsion between the atoms, due to the electric charges of their nuclei and electrons.

The attractive forces between the molecules in a solid provide its characteristic elastic or stretchy properties. When we stretch a solid, we are slightly increasing the spacing of it molecules.

The tension we can feel in a stretched spring is due to all the forces of attraction between the molecule in the spring.

Possible variables: I could change

• Material of spring
• Length of spring

Variables I will study: I will study the mass of load.

How I will make my test fair and why: To make sure my investigation is as fair as possible I will do a number of things.

Firstly I will make sure that an equal amount of mass (100g each time) is added each time. Then I will make sure that the readings are taken accurately, by using a splint to measure and mark the exact millimetre on the ruler.

I will also make sure the spring is as close to the ruler as possible and also hanging off the table if the weights exceed past it to, make sure I get an accurate reading. As if it leans on the desk it could effect the extension and the deformation of the spring.

If I have to do the experiment the next day I will make sure that the spring I use is put in a separate place, because the used spring may start to become deformed. If we used a new spring our results could be effected.

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