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By Rachel McGreevy Aim The objective of my practical investigation is to find out whether the temperature of an elastic band affects its elasticity, as well as its tensile strength. Before I started the investigation, I carried out some research on what elastic bands are made out, and how and why they act like they Young s modulus of a metre ruler at normal temperature, to form my own hypothesis on the outcome of my experiment.
Abstract To test whether temperature of an elastic band affects its behaviour I will be carrying out 3 experiments with 7 different temperatures, ranging from 20 Degrees Celsius to 80 Degrees Celsius. The first experiment will test how the tensile strength of the band will be affected, by testing the breaking weight of the band.
The second third experiments will test how the elasticity and extension of the band will change in the same range of temperatures. Introduction to Background Physics Elastic bands can be found in almost every household all over the world, varying in size, shape and thickness.
Rubber bands are made mainly from a mix of rubber and latex, along with various chemical solutions, which are then poured into an extrusion machine. This extrudes the compounded rubber into a tube shape, which is then set and finally cut width-ways to create the shape of the elastic bands commonly used today1.
Rubber is a polymer, which is a chain of interlinked monomers. In particular, rubber is a type of polymer called an elastomer, which is a large molecule that can be stretched to around twice its size, and still return to its original shape.
When a force is placed on the elastic band, the tangled up chains of monomers untangle, letting the material stretch. When the force is taken off the rubber band, the chains of monomers tangle up again into their original forms.
However, the larger the force on the rubber band the less the molecules will tangle up again 2. The entropy of a material is a measure of order of the molecules in a material, where the more disordered the molecules are, the higher the entropy is 3.
When a material is heated, the molecules that the material consists of have more energy and so tend to spread out and travel with more speed. Therefore the higher the temperature of the material, the higher the entropy of becomes due to the spreading out and therefore disorder of the molecules.
Usually, materials tend to expand when they are heated; however due to the structure of the rubber in the elastic bands which is formed by tangled chains of monomers, when the bands are heated they tend to get smaller in size.
This is because the monomers in the material have more energy and are moving around with a greater speed, and so the chains become more tangled, and so entropy is increased.
This means that as the chains are more tangled causing them to pull tighter together, and therefore the rubber band will contract 4. Because the rubber band contracts when heated, the higher the temperature of the rubber band, the harder it is to stretch the rubber band.
This should mean that rubber bands at higher temperatures will take more weight to break, but extend less than rubber bands at lower temperatures. We can explain this further by looking at the energy in the elastic band when it is stretched.
When an elastic band is stretched, it will seem to heat up. This can be observed by holding a rubber band on your top lip and stretching it. You will notice a positive change in temperature during and for a short time after the stretch.
You will also notice that the band will become cooler when it is released from the stretch, as it absorbs heat causing its surrounding environment to cool down. This change in temperature can be explained using Gibbs free energy equation, using the entropy and enthalpy of the elastic band.
As explained above, the entropy of a material is a measure of the disorder of the molecules. The enthalpy of a material is the total energy change of the system, from when the elastic band is relaxed to when the band is stretched.
Enthalpy is determined by the internal energy of the system, as well as its pressure and volume5. Before looking at the values of entropy and enthalpy of a system, it is important to know whether it is a spontaneous process or not.
A spontaneous process is one where free energy is produced without an external source of energy driving it. In the system of the elastic band, we are stretching it which is a form of external energy, and so the system is non-spontaneous 6.
When the process is reversed and the elastic band is released from the stretch, no external source of energy is being put into the system when the band goes from a stretched to relaxed state; therefore this system is a spontaneous process. As the system is spontaneous, the process needs energy to happen, drawing energy from surroundings which will then cool down 7.
This means that the energy gained by the system is larger, and so each individual molecule will have more energy. This means that as explained before, the chains of monomers become more tangled, causing the heated rubber band to contract and become harder to stretch.Determine the Young modulus of a material The extension is very small and, using a metre ruler, we get only one significant figure.
Plotting the mass added against extension for the gradient means that we might trust two significant figures although one significant figure is strictly correct. How accurately a measurement of the Young's modulus can be made depends upon the accuracy to which Mg, mg, y, L, b and d can be measured.
A classroom ruler might only measure y, b and d to the nearest millimeter. The symbol for Young's modulus is usually E from the French word élasticité (elasticity) but some prefer Y in honor of the man himself. Young's modulus is defined for all shapes and sizes by the same rule, but for convenience sake let's imagine a rod of length ℓ 0 and cross sectional area A being stretched by a force F to a new length ℓ 0 + Δ ℓ.
A modulus of elasticity of the Wire, called Young’s modulus (E), is defined as the ratio It should be noted that Young’s modulus, E, is calculated from the ratio stress: strain only when the wire is under ‘elastic’ conditions, that is, the load does not then exceed the elastic limit.
May 08, · There is no such standard material as "human bone". The strength of the human bone depends on too many factors (type of bone, location on one given bone, age, diet, diseases etc.) to have one general Young's timberdesignmag.com: Resolved.
Aim of this experiment is to find the Young's modulus of the given material by uniform bending using pin and microscope method.