Define Hooke's law of elasticity, proportionality, permanent set and b

1.	Define Hooke's law of elasticity, proportionality, permanent set and breaking stress.
Answer» Solution :Hooke.s Law : If states that within elastic limit, stress is proportional to strain. `"i.e., stress"prop"strain"rArr("stress")/("strain")="constant(E)."` This constant is called elastic constant `(E).` Proportionality limit : When load is incresed the elongation of the wire will also increases. The maximum load upto which the elongation is directly proportional to the load iscalled PROPOR- tionality limit `(A).` The graph DRAWN between load and EXTENSION. It is straight line .OA.. Permanent set : If the load on the wire is increased be- yond elastic limit, the elongation is not pro- portional to load. On removal of the load the wire cannot regain its original LENGTH. The length of the wire increases permanently. In figure permanent set is given byOP. This is called permanent set. Breaking stress : If the load is incresed beyond yield poin the elongation is very rapid, even for small changes in load and wire becomes THINNER and breaks. This is shown as E. The breaking force per unit area is called breaking stress.

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