Knowledge of Physics

Q.1.)  What is Young's modulus of elasticity? Derive expression for it. Ans:  Young's modulus: If the restoring force developed in  a body is normal to its cross-section area, the stress due to such force is called normal stress. Normal stress is produced in a body when there is longitudinal or volumetric strain. Young's modulus of elasticity of a material is defined as the ratio of normal stress and longitudinal(or linear) strain. From fig.1, if F is the external force applied to the body of cross-section area A, and original length `l_0` with change in length(extension or compression) `\Delta l` produced on it, then  ...................(1)        We have, Normal Stress = `\frac{F}{A}` ........(2) and Longitudinal Strain = `\frac{l_1 - l_0}{l_0} = \frac{\Delta l}{l_0}` ........(3)  Using (2) and (3) in (1), `Y = \frac{\frac{F}{A}}{\frac{\Delta l}{l_0}}`     = `\frac{F \times l_0}{A \times \Delta l}`   `\therefore` Y = `(\frac{...

 Q.1.)  List the general properties of matter. Ans: Some properties of matter which are common to all states of matter can be listed as below. Matter occupies certain space and possesses mass in all states. matter possesses inertia, that is, inability to change its state by itself. matter in all states is divisible into smaller portion. The smallest particle of matter is called molecule. molecules are formed by single or multiple atoms. Matter possesses adhesive and cohesive forces. The force of attraction between molecules of same matter is called cohesive force while force of attraction between molecules of different matters is called adhesive force. Matter in all states possesses elasticity, that is, the property due to which the body regains its original same and size after removal of deforming force applied on the body. Matter possesses compressibility. Three states of matter, that is, gas, liquid and solid, has the degree of compressibility in following order: gas > l...