Investigate whether elastic bands and springs behave the same way.
When a load(weight) is applied to either an elastic band or a spring, do they return to their original length i.e. is the extension directly proportional to the load.
BACK GROUND INFORMATION:
The structure of elastic bands and springs are different. By studying a Newton metre, I noticed that the marks between each Newton applied were equidistant. This implies that a spring returns to the original length, therefore the load and length are directly proportional. This is because the structure of a spring is coiled. Therefore the molecules have been twisted and pulled apart, this creates the spring, as the molecules try to pull themselves back together. An elastic band is made of polymers.
Hooke's Law states when a material is stretched, the change in length is directly proportional to the stretching force applied. However when an elastic limit is reached the material will be deformed and no longer obey the law. When a material is stretched, the molecules are pulled further away from each other, weakening the bonds, if the bonds break then the molecules cannot return to their original state. This is known as the elastic limit. Therefore, the number of molecules will effect the elastic limit of a material. The more molecules there are the more energy is needed to weaken the bonds. When a load is applied this creates gravitational potential energy(g.p.e). Therefore, materials smaller in width and length need less weight for the elastic limit to be reached.
There are several variables which when altered will effect the behaviour of elastic bands and springs. To make a fair procedure their are certain variables that need to be controlled, and others that need to be varied in order conduct the experiment and give a detailed conclusion.
The room temperature will effect the experiment, if it drops the particles will vibrate less, and will be drawn closer to each other, meaning the bonds will be harder to break and the material will contract. However if the temperature is raised then the heat energy will be transferred to the molecules, as the molecules vibrate more the bonds to weaken, resulting in the material expanding and become more stretchable. The bonds will also weaken if the band has been used frequently (this will heat the band and spring as well), to prevent this I will use 3 different elastic bands and springs of the same size and width. Due to limited resources I cannot control the temperature, therefore preventing me from experimenting with this variable.
A possible variable I could alter is the width, size or cross sectional area. This will require different amounts of energy to stretch the band or spring. If the width and size increase then more weight is needed to create more gravitational potential energy in order to separate the bonds. However I have decided not to use this variable, as the range of results would be limited because it would be difficult to alter these variables to a large degree.