Mechanics 3 Flashcards
Define plastic bodies
Bodies which do not return at all to its original dimensions after removal of deforming force are called plastic bodies/materials.
Define perfectly elastic bodies
Some bodies/materials that return exactly to its original dimensions after removal of external deforming force. They are called perfectly elastic bodies or materials.
Define elasticity
The property by virtue of which material bodies regain their original dimensions on removal of deforming force is called elasticity.
Define plasticity
The property of material to undergo permanent deformation even after removal of external deforming forces is known as plasticity.
Define deformation
The change in shape, size or both of a body arising due to external force is called deformation.
Define deforming force
The force responsible for deformation of a body is called deforming force.
Why is deformation produced in a body?
Deformation is produced in a body due to change in relative positions of molecules within the body due to applied deforming force.
Define Stress
Stress is defined as applied force per unit cross sectional area of the body.
Define longitudinal stress
When applied force/ deforming force produces change in length of a body, the stress associated is called longitudinal stress or tensile stress.
Define volume stress
If a deforming force produces change in volume of a body, the stress associated is called volume stress.
Define shearing stress
If the deforming force produces change in shape of the body, the stress associated with it is called shearing stress.
Define strain
Strain is defined as the change in dimensions per unit original dimensions.
Define longitudinal or tensile stress
Longitudinal or tensile strain is defined as the ratio of change in length to original length.
Define volume strain
Volume strain is defined as the ratio of change in volume to original volume.
Define shearing strain
Shearing strain is defined as the ratio of relative displacement of any layer to perpendicular distance from fixed layer.
State Hooke’s law
Provided the elastic limit is not exceeded, deformation of a material is proportional to the force applied to it,
Define modulus of elasticity
Modulus of elasticity of a material is defined as the slope of stress-strain curve in the elastic deformation region.
Define elastic limit
The maximum value if stress up to which stress is directly proportional to strain is known as the elastic limit.
What is set?
If the elastic limit is exceeded, then the body does not preserve its original dimensions after removal of external, deforming force and acquires a perfect deformation ‘set’.
Define Young’s modulus (elasticity of length)
Young’s modulus is the ratio of longitudinal stress to longitudinal strain.
Why is Young’s modulus of elasticity only a property of solids?
Only solids have length.
Define Bulk modulus (Volume elasticity)
Bulk modulus is defined as the ratio of the volume stress to the volume strain.
Young’s modulus is high for ________.
Materials with strong interatomic bonds.
Define compressibility
The reciprocal of the Bulk modulus of elasticity is called compressibility of the material.