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An Investigation into the relationship between the forces applied to a length of wire and its extension.

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Physics Coursework An Investigation into the relationship between the forces applied to a length of wire and its extension. Aim: - To investigate the relationship between the extension [e] of a length of copper wire and the force [f] applied to the wire, to do this I intend to use Hooks law the linear modulus is known as stress/strain, also known as Young's modulus [E]. I hypothesise tat as we increase the amount of force applied to the wire, so its extension will increase. As this was what I found in previous experiments involving Hooks law. Diagram: - I will use Young's modulus as it links the two factors that we wish to investigate in that to find a value for Youngs modulus you need to find two values, stress and strain E = Stress where; - stress = Force [f] also;- Strain = extension [e] Strain Cross sectional area [a] original length [l] As we can see from above stress is calculated using force and cross sectional area there for involving force as we require, this will be my input variable and will be the value subject to change. ...read more.


i predict that the relationship between the two will be proportional. I have decided upon this outcome due to my background reaserch into the matter. I found that when streching metals a modulus applies called youngs modulus, this tells us that when streching a wire we get a graph of stress against strain where stress is equall to load/crossectional area therefore incorporating load and strain is equal to extension/original length. Advanced Physics by tom duncan states that tensile strain is directly proportional to tensile stress during elastic deformation. This statment is known as hookes law The outcome graph looks like this:- we can see a proportional relationship between the two variables at the beggining of the graph due to the constant gradient, a6t piont b we can see the graident is constantly changing. here youngs modulus no longer applies because the material has passed its elastic limit. i think that me graph of oad/extension will be very simular provided the other factors involved remain constant, these are cross sectional area and original length. To do this i intend to take multiple readings of the crosssectional area of the wire throughout the experiment to find an avrage as i know that the wire will become thinner as i strech it, as i descoverd in my preliminary tests. ...read more.


these allowed an exterrmly accurate measurement as small as 0.25mm and allowed us to measue lenghts as large as 10cm this was far larger than the required amount. To carry out the experiment i would use the apparatus in a way shwn in the above diagram (fig 1). this method was the best for me to use as it was implamentable as we had all the required equipment to hand, Although i did find some other methods in my research that would provide a more accurate set of results. i found it to be more accurate because the experiment was suspended from the celing and the wire was entrly vertical. unfortunatly this method was unimplamentable due to lack of equipment, i found the main reason why my method was less accurate was because the force was applied by the weight to the wire in a vertical irection but the majoraty of the wire ran horizontaly along the desk therefore the force as not properly tranfered through all the wire this was shown in my perliminary results because we set up another pointer near the weight and measued extension here it showed that the extension was far greater near the weight than near the clamp where we were measuring it. i also found that other factors infuencing my results were 'necking and creeping' Results:- ...read more.

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