Question

HEYAAA,,,,,,

STATE HOOKE"S LAW...

ANSWER IN CUTE AND UNDERSTANDING WAY...:)

Answer 1

It states that within the limit of elasticity, the stress induced (σ ) in the solid due to some external force is always in proportion with the strain (ε ). In other words the force causing stress in a solid is directly proportional to the solid's deformation. Consider a spring with a spring constant k that is stretched with a force F extends to a distance x with reference to the initial position.
Force required for deformation x is given by

F = -Kx



The determination of elastic modulus E from the tensile experiment results is depicted in the figure.
It can be seen from the graph that the curve of stress versus strain is linear within the limit of elasticity of the material. It is inferred that for the load below the limit of elasticity, the stress induced is in proportion with the strain in the solid.

Hook's law tells about linear realtionship between stress and strain of CERTAIN ELASTIC materials. That is within PROPORTIONALITY LIMIT, stress is proportional to strain.
Now why certain elastic materials? This is because, elasticity means regaining original shape after removal of load. So elasticity does not speak anything about linear relationships about stress and strain. This is why an elastic material may not obey Hook's law. Rubber does not obey Hook's law. But the materials which obey Hook's law are elastic materials. So I used the words CERTAIN ELASTIC MATERIALS.
Now about PROPORTIONALITY LIMIT. If you look into the stress strain relationship of mild steel and many other materials, you will see stress is proportional to strain upto a certain limit. This is the proportional limit. After that point the relationship does not remain linear, yet the stress is within elastic limit, that is on removal of load strain will be zero. However the proportionality limit and elastic limit are hard to distinguish, hence for simplifications sometimes they are assumed to be the same point.
So keep in mind while applying Hook's law, CERTAIN ELASTIC MATERIALS, and PROPORTIONALITY LIMIT.


hope it helped u...NAVI

Answer 2

Hi

Here is ur answer

HOOKE'S LAW:

  Within elastic limit, stress developed in body is directly proportional to the strain produced init.

According to this law,

    Stress ∝ Strain

Therefore,   Stress = C.Strain

     C = Stress / Strain

 Within elastic limit the ratio of stress to the strain is constant. This constant is called elastic constant or modulus of elasticity. This constant depends upon the material of the body.

Therefore,

 $ Modulus of elasticity = Stress / Strain

# Its SI - unit is N/m².

# Dimension is [M¹L⁻¹T⁻²]

Hope it helps U