Slide 1Physics Study Program Faculty of Mathematics and Natural Sciences Institut Teknologi Bandung
FI-1101
Materi Hari Ini
Elastisitas
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Real rigid bodies are elastic we can slightly change their dimensions
by pulling, pushing, twisting or compressing them.
Stress: Deforming force per unit area
Strain: Unit deformation
Shearing stress
Hydraulic stress
Elastic modulus: describes the elastic behavior (deformations) of objects
as they respond to forces that act on them
Physics Study Program - FMIPA | Institut Teknologi Bandung
(1) Stress = cte x Strain Recovers original dimensions when stress removed.
(2) Stress > yield strength Sy specimen becomes permanently deformed.
(3) Stress > ultimate strength Su specimen breaks.
Tension and compression:
( F= force applied perpendicular to the area A of the object)
( fractional change in length of the specimen)
Stress = (Young’s modulus) x Strain
Shearing:
( fractional change in length of the specimen)
Units of Young modulus: F/m2
Stress = (Shear modulus) x Strain
Hydraulic stress:
Young’s Modulus
Shear Modulus
Shear moduli and Young moduli are comparable in magnitude for most materials
(Liquids have zero shear modulus)
Physics Study Program - FMIPA | Institut Teknologi Bandung
Pressure and Bulk Modulus
Unit of pressure is N/m2 = Pascal (Pa)
Atmospheric pressure ~ 105 Pa= 15psi
1 psi = 1 pound per square inch
Bulk modulus B relates fractional volume change to pressure change
Physics Study Program - FMIPA | Institut Teknologi Bandung
Stress, Strain and Hooke’s law
F/A or pressure are known as “stress”
Fractional changes in length or volume are known as “strain”
Above relations between stress and strain account for “elastic” behavior and Hooke’s law
Physics Study Program - FMIPA | Institut Teknologi Bandung
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