Testing
Hooke’s Law
By Daniel Bowman 11CU
Introduction
Hooke’s law is when forces applied to a solid object and it can result in extension or compression. Hooke’s law is able to predict how a stretchable object would behave when a force is applied to it.
Planning
I aim to show how much force strips of black bin liners (polythene) will take before it reaches its elastic limit and obey Hooke’s law. I will also investigate if the length of the strips can alter the results, keeping the width the same.
The main suitable equipment I will need to use may include the two different types of plastic cut at different lengths and 100g masses to test the extension. I will obviously need other basic apparatus to carry out the investigation. My experiment will last until each strip of plastic splits, so I cannot at this time state how many masses I will require.
Polythene
The plastic I have chosen to use has many uses. Polythene is used to manufacture bottles, carrier bags, buckets, machine parts and bowls. This suggests to me that thickness of the plastic can affect the strength, as a plastic carrier bag is not as strong as a plastic bucket. I also no that there are two types of polythene: High density, which is rigid and hard, and low density, which is tough and flexible. Machine parts are generally made from high-density polystyrene whilst bottles are made from the low-density polystyrene.
The Chemistry of Plastics
In metals molecules arrange themselves into crystalline lattices. Polymers have molecules arranged into long strings of molecules.
Carbon is contained in all organic materials and can be easily liked to other materials such as hydrogen and oxygen because of its need to find four electrons. Carbon is the main ingredient in the long chained polymer molecules and forms covalent bonds with other materials. This carbon chain is known as the polymer backbone.
