ELASTIC LIMIT

A lift of mass 'm' is connected to a rope which is moving upward with maximum acceleration 'a'. For maximum safe stress, the elastic limit of the rope is 'T'. The minimum diameter of the rope is (g = gravitational acceleration)

Materials get deformed when force is applied. Some of them regain their status when the applied force is removed. They are termed as elastic. Those of which not regaining are called plastic. There may be delay in the regaining in some materials. They are said to have got elastic aftereffect, since they have gone beyond the elastic limit. Repeated application and removal of force leads to fatigueness in the material. Fatigued materials may break at any point time and so are avoided. The stress strain graph for two materials A and B is shown in the following figure: The strength of the material A and B is S_(A) and S_(B) , respectively, while the longevity of plastic behaviour is L_(A) and L_(B) . Then

In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as (a) If both assertion and reason are true and reason is the correct explanation of assertion. (b) If both assertion and reason are true but reason is not the correct explanation of assertion. (c ) If assertion is true but reason is false. (d) If assertion and reason are false. Q. Assertion: The materials which have very small range of plastic extension are called brittle materials. Reason: if the stress is increased beyond the elastic limit, the material will break.

The elastic limit of an elevator cable is 2xx10^(9) N//m^(2) . The maximum upward acceleration that an elevator of amss 2xx10^(3)kg can have been supported by a cable would not exceed half of the elastic limit would be

A wire of uniform cross-sectional area A and young's modulus Y is stretched within the elastic limits. If s is stress in the wire, the elastic energy density stored in the wire in terms of the given parameters is

According to Hooke's law, within the elastic limit stress/strain = constant. This constant depends on the type of strain or the type of force acting. Tensile stress might result in compressional or elongative strain, however, a tangential stress can only cause a shearing strain. After crossing the elastic limit, the material undergoes elongation and beyond a stage beaks. All modulus of elasticity are basically constants for the materials under stress. If stress/strain is x in elastic region and y in the region of yield, then