1.

State Hooke's law of elasticity.

Answer» <html><body><p></p>Solution :Hooke.s low is for a small deformation, when the stress and strain are proportional to each other. it can be verified in a simple way by stretching a thin straight wire (stretches like spring) of <a href="https://interviewquestions.tuteehub.com/tag/length-1071524" style="font-weight:bold;" target="_blank" title="Click to know more about LENGTH">LENGTH</a> L and <a href="https://interviewquestions.tuteehub.com/tag/uniform-1437485" style="font-weight:bold;" target="_blank" title="Click to know more about UNIFORM">UNIFORM</a> cross sectional area A suspended from a fixed point O. A pan and a pointer are attached at the free and of the wire. The extension produced on the wire is measured using a vernier scale arrangement. the experiment shows that for a given load, the corresponding stretching force is <a href="https://interviewquestions.tuteehub.com/tag/f-455800" style="font-weight:bold;" target="_blank" title="Click to know more about F">F</a> and the elongation produced on the the wire is`DeltaL`. It is directly proportional to the original length L and inversely proportional to the area of cross section A. A graph is plotted using F on the x-axis and `DeltaL`on the y-axis. <br/> Therefore, `DeltaL = ("slope")F` <br/> Multiplying and dividing by volume, <br/> `V = AL` <br/> `F("slope") = (AL)/(AL)` <br/> Rearranging, we get `F/A = (L/(A("slope")))(DeltaL)/(L)` <br/> Therefore, `F/A prop ((Delta L)/(L))` <br/> Comparing with stress and strain equations, `sigma prop epsilon`. I.e., the stress is proportional to hte strain in the elastic limit. <br/> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/FM_PHY_XI_V02_C07_E01_045_S01.png" width="80%"/> <br/> Stress- strain profile curve : The stress versus strain profile is a plot in which stress and strain are noted for each load and a graph is drawn taking strain along the X- axis and stress along the Y- axis. The elastic characteristics of the materials can be analysed from the stress -strain profile. <br/> (a) Portion OA: in this reason, stress is very small such that stress is proportional to strain, which means Hook.s law is valid. The point A is called limit of proportionality because above this point Hook.s law is not valid. The slope of the line OA gives the Young.s modulus of the wire. <br/> (b) Portion AB: the reason is reached if the stress is increased by a very small amount. In this reason, stress is not proportional to the strain. But once the stretching force is hence, the point B is known as yield point (elastic limit). The elastic hebaviour of the material (here wire) in stress-strain curve is OAB. <br/> (c ) Portion BC: if the wire is stretched beyond the point B (elastic limit), stress increases and the wire will not regain its original length after the <a href="https://interviewquestions.tuteehub.com/tag/removal-1184751" style="font-weight:bold;" target="_blank" title="Click to know more about REMOVAL">REMOVAL</a> of of stretching force. <br/> (d) portion CD: with further increase in stress (beyond the point C), the stress increases rapidly and reaches the point D. Beyond D, the strain increases even when the load is <a href="https://interviewquestions.tuteehub.com/tag/removed-2986295" style="font-weight:bold;" target="_blank" title="Click to know more about REMOVED">REMOVED</a> and brakes (raptures) at the point E. Therefore the maximum stress (here D) beyond which the wire breaks is called breaking stress tensile strength. The corresponding point D is known as the fracture point. The reason BCDE represent the plastic . <br/> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/FM_PHY_XI_V02_C07_E01_045_S02.png" width="80%"/></body></html>


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