Unit-5 Pressure and Deformation in Solids
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Unit-5 Pressure and Deformation in Solids
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Answer: In elastic deformation the body regains its original shape and size when the load is removed.
Answer: Plastic deformation is permanent; the body does not return to its original shape.
Answer: Stress = F/A; it measures the internal force per unit area produced in a body.
Answer: Strain = (change in length)/(original length); it is a dimensionless ratio.
Answer: Strain = change in length / original length = 0.004 m / 2 m = 0.002.
Answer: Within the elastic limit, F is directly proportional to x, so the extension increases linearly with the load.
Answer: This proportionality (stress = Young's modulus x strain) is Hooke's law in terms of stress and strain.
Answer: Beyond the elastic limit the material deforms plastically and does not return to its original shape.
Answer: Young's modulus Y = stress/strain, and it measures the stiffness of a material.
Answer: Stress = F/A = 100/0.001 = 10^5 Pa; Y = stress/strain = 10^5/0.0005 = 2 x 10^8 Pa.
Answer: k = F/x, the force needed to extend the spring by one unit of length.
Answer: k is a property of the spring itself (material, length, wire thickness), not of the load applied.
Answer: k = F/x, so its unit is N/m.
Answer: Stress = force/area, giving the unit N/m^2 = pascal.
Answer: k = F/x = 20/0.1 = 200 N/m.
Answer: Because extension is directly proportional to load, the graph is a straight line through the origin.
Answer: x = F/k = 10/50 = 0.2 m.
Answer: Both are force per unit area, so both are measured in pascals.
Answer: Strain is the ratio of two lengths, so it has no unit.
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Answer: Stress = F/A = 500/0.01 = 50,000 Pa.