# Rubber Band Investigation Essay

I am going to investigate the extension of a rubber band, which I will submit to increasing Newton’s of force being applied in the form of 1N weights.PlanI will set the experiment up as follows:The rubber band will be attached to a retort stand, I will measure the starting size of the rubber band and then I will measure it three separate times adding 1N of force each time.I will continue this process until 10N’s where I shall stop, to avoid Hooke’s law coming into place.To make it a fair test we are repeating each level of force added 3 times, swapping the weights in between each measurement.We will take an average by adding the 3 results together and then dividing by the total amount of results. If any results which are anomalous or out of place occur I will retake these results to make a more accurate overall result.We aim discover a steady increase in the extension of the rubber band, as increasing amounts of force are applied.A key factor that needs to be controlled is how much the rubber band has been stretched from one set of 1-10 Newton’s results to the next. Hopefully this will not be a problem because the rubber band will not reach its limit of elasticiticty until after 10 Newton’s of force being applied.Extra InformationThe Law of elasticity discovered by the English scientist Robert Hooke in 1660, which states that, for relatively small deformations of an object, the displacement or size of the deformation is directly proportional to the deforming force or load. Under these conditions the object returns to its original shape and size upon removal of the load.Elastic behavior of solids according to Hooke’s law can be explained by the fact that small displacements of their constituent molecules, atoms, or ions from normal positions is also proportional to the force that causes the displacement.The deforming force may be applied to a solid by stretching, compressing, squeezing, bending, or twisting. So a rubber band exhibits elastic behavior according to Hooke’s law because the small increase in its length when stretched by an applied force doubles each time the force is doubled.Mathematically Hooke’s law states that the applied force F equals a constant k times the displacement or change in length x, or F = kx. The value of k depends not only on the kind of elastic material under consideration but also on its dimensions and shape.At relatively large values of applied force, the deformation of the elastic material is often larger than expected on the basis of Hooke’s law, even though the material remains elastic and returns to its original shape and size after removal of the force. Hooke’s law describes the elastic properties of materials only in the range in which the force and displacement are proportional. Sometimes Hooke’s law is formulated as F = -kx. In this expression F no longer means the applied force but rather the equal and oppositely directed restoring force that causes elastic materials to return to their original dimensions.No strict safety precautions need to be used only obvious light precautions are necessary, as the only potential danger would be if the rubber band snapped, however this will not happen if there is no more than the maximum load on the spring of 10N at any one time.This will also remove the problem of the stand on which the experiment is taking place from falling over.1. At this point the limit of proportionality has been reached this is where Hooke’s law is no longer accurate.2. This point is the rubber band’s elastic limit if the force is removed from the bandit will no longer return to its original shape.Safety precautions* Be sure to keep your feet out of the area in which the masses will fall if the rubber band breaks!* Be sure to clamp the ring stand to the lab table, so that the mass does not pull it off the table.* You need to hang enough mass to the end of the spring to get a measurable stretch, but too much force will permanently damage the band.** Hooke’s Law says that the stretch of a spring is directly proportional to the applied force. say “Stress is In symbols, F = kx, where F is the force, x is the stretch, and k is a constant of proportionality. If Hooke’s Law is correct, then, the graph of force versus stretch will be a straight line.I will start with the zero end of the ruler even with the bottom of the rubber band when the spring scale is hanging on the rubber band. This will allow the change in length of the rubber band to be easily determined.Apparatus I will use:1 retort stand3 rubber bands10*1 Newton weightsRulerMy input variable is force in Newton’s applied and my output variable is extension of rubber band.PredictionI predict that after 10 N of force has been applied to the rubber band it will reach its elastic limit and then it will start to follow Hooke’s law, where the amount the rubber band is stretched out of shape past its original size.I also predict that the greater the weight applied to the band, the further the band will stretch. This is because extension is proportional to load and so if load increases so does extension and so stretching distance.I also predict that the results will produce a straight-line graph and if I were to continue the experiment to further study the elastic limit I predict the graph would flatten out after 11 Newton’s were the rubber band would be stretched out of shape, or Hooke’s law would come into play.Extension = New length – Original lengthto see if my prediction is correct I will experiment, and obtain results using Hooke’s Law. He found that extension is proportional to the downward force acting on the rubber band.Hooke’s LawF=kxF = Force in Newtonk= Rubber band constant proportionalityx = Extension in CMMethod1. I set up the retort stand as shown in diagram 1 I put my blazer on the floor to protect the tiles in the case of the rubber band reaching its elastic limit and snapping.2. I also fastened the retort stand to the table with a clamp instead of my original plan of just weighing the stand down with my textbooks!3. I measured the starting length of the elastic band and then hung the band form the claw of the retort stand , I then added increasing amounts of force by adding extra weights.4. I then measured the increase or extension of the rubber band from its original size.5. I then removed the weights and put them back on and then recorded the results to further times to get and average and a more accurate set of results.6. I then repeated this procedure for 2,3,4,5,6,7,8,9 and 10 Newton’s of force and measured the extension of the rubber band.7. I then decided to try to further investigate Hooke’s law by actually going past 10 Newton’s of force to find the elastic limit of the rubber band, (when the rubber band snaps!)8. I then averaged out all my results and produce a graph, were I could see a line of best fit and prove my prediction was right.ConclusionAfter doing this investigation I was very happy with how it went, the practical was performed efficiently and we even had time to add and experiment to test the rubber bands elastic limit.I proved the hypothesis to be correct and I also proved my prediction was an accurate prediction of what happened.I learnt a lot about Hooke’s law and elastic limits as a result of this investigation and I feel it was a worthwhile investigation in helping me to understand about elastic limits.By analysing my results I have proved my predication right that there will be an increase in the length of the rubber band as you increase the amounts of weights added.I was also completely correct that the rubber band would have limit of elasticity at about 10N of force where it will be permanently out of shape this increase in rubber band size did occur as predicted.The thing that Surprised me about my final results was the fact that the bands did not snap until 13.5Newtons of force were applied, I predicted the limit of the bands to be in the region of 10-12Newtons of force, not 13.5.To analyse these results with my scientific knowledge I would have to say the increase in length of rubber band is directly proportional to the increase in force applied so stretching distance also increases.We did alter are plan slightly because we had extra time at the end we tested the limit of elasticity to try to prove or disprove Hooke’s law.By analyzing my graphs with my scientific knowledge I can work out that the more force applied to the band, the greater the extension, that is why both my graph get gradually taller instead of ascending if you wanted to produce an ascending graph you could start off with 10 Newton’s of force applied and keep taking more weights off to lower the extension.From my double rubber band experiment you can clearly see there is less extension throughout because with two bands they can share the force applied thus with two bands there is a higher elastic limit then with just one rubber abnd.Overall I am pleased with the outcome of this Investigation I believe that I have proved Hooke’s law to be correct and that after the limit of elasticity the rubber band is permanently put out of shape.