Class 11 Physics - BIHAR
Mechanical Properties of Solids
The chapter 'Mechanical Properties of Solids' in Class 11 Physics explores how solid materials behave when subjected to external forces. Students learn about elasticity, plasticity, and how materials deform under stress and strain. Key topics include Hooke's Law, Young's modulus, bulk modulus, shear modulus, and elastic potential energy stored in stretched wires. For Bihar Board (BSEB) students, this chapter is crucial as it forms the foundational mechanics required for understanding structural engineering concepts. It regularly features in both objective and long-answer questions in the annual physics board examinations.
Start Learning FreeKey Concepts
Elasticity and Plasticity
Elasticity is the property of a body to regain its original shape after the removal of a deforming force, whereas plasticity is the inability to do so.
Stress and Strain
Stress is the restoring force per unit area set up inside a material, and strain is the fractional change in dimensions caused by that stress.
Hooke's Law
Within the elastic limit, stress is directly proportional to strain, meaning the ratio of stress to strain remains constant (Modulus of Elasticity).
Elastic Moduli
Different types of stress and strain lead to three moduli of elasticity: Young's modulus (length), Bulk modulus (volume), and Shear modulus (shape).
Elastic Potential Energy
Work done in stretching a wire is stored inside it as elastic potential energy, which can be calculated using the force and elongation.
Important Formulas
Board Exam Info
In the Bihar (BSEB) Class 11 Physics examination, this chapter typically carries around 4 to 6 marks. Questions usually include 1-2 objective (MCQ) questions, a short-answer question defining elasticity or Hooke's law, and occasionally a numerical problem based on Young's modulus or elastic potential energy.
Frequently Asked Questions
Which is more elastic, steel or rubber?
Steel is more elastic than rubber because for a given deforming force, the strain produced in steel is much less than in rubber, meaning its Young's modulus is higher.
Why is stress a tensor and not a vector?
Stress is not a simple vector because at any point inside a solid, it has magnitude and direction relative to the orientation of the surface area on which it acts.
What is the unit and dimensional formula of Young's Modulus?
The SI unit of Young's Modulus is Pascal (Pa) or N/m², and its dimensional formula is [M¹L⁻¹T⁻²].
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