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Questions and Answers
What distinguishes liquids from solids based on their molecular arrangement?
What distinguishes liquids from solids based on their molecular arrangement?
- Liquids have fixed molecular centers, while solids have free-moving centers.
- Liquids display short-range order, while solids show long-range order. (correct)
- Liquids and solids both exhibit long-range order but differ in vibrational amplitude.
- Liquids exhibit long-range order, whereas solids only have short-range order.
A material strained beyond its elastic limit will return to its original dimensions once the stress is removed.
A material strained beyond its elastic limit will return to its original dimensions once the stress is removed.
False (B)
If a shear force of 50 N is applied to the top surface of a cube with sides of 0.5 m, fixed to a table, calculate the shear stress?
If a shear force of 50 N is applied to the top surface of a cube with sides of 0.5 m, fixed to a table, calculate the shear stress?
200 Pa
The property of a fluid that measures its resistance to deformation under shear stress is known as ______.
The property of a fluid that measures its resistance to deformation under shear stress is known as ______.
Match the types of materials with their behavior under stress:
Match the types of materials with their behavior under stress:
A spherical object experiences a pressure increase. Which modulus is most relevant to determine the changes in volume?
A spherical object experiences a pressure increase. Which modulus is most relevant to determine the changes in volume?
Liquids are considered incompressible because their volume does not change under pressure.
Liquids are considered incompressible because their volume does not change under pressure.
Calculate the pressure at the bottom of a swimming pool that is 3 m deep, assuming Patm = 1.013 x 10^5 Pa and $ρ$water = 1000 kg/m³?
Calculate the pressure at the bottom of a swimming pool that is 3 m deep, assuming Patm = 1.013 x 10^5 Pa and $ρ$water = 1000 kg/m³?
The phenomenon where pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid and to the walls of the container is known as ______'s principle.
The phenomenon where pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid and to the walls of the container is known as ______'s principle.
Why does a sphygmomanometer, used for measuring blood pressure, need to apply external counter-pressure on an artery?
Why does a sphygmomanometer, used for measuring blood pressure, need to apply external counter-pressure on an artery?
Flashcards
Shear Stress
Shear Stress
Force acting tangent to a material surface divided by the area over which the force acts.
Shear Strain
Shear Strain
Ratio of the change in length to the original length when a stress is applied.
Shear Modulus
Shear Modulus
Measure of a material's resistance to deformation by shear stress.
Young's Modulus
Young's Modulus
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Bulk Modulus
Bulk Modulus
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Plastic Behavior
Plastic Behavior
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Elastic Limit
Elastic Limit
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Density
Density
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Pressure
Pressure
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Fluid pressure
Fluid pressure
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Study Notes
- Lecture focuses on elasticity, stress, and strain within solids and fluids
Learning Goals
- Stress
- Strain
- Young's Modulus
- Shear Deformation
- Volume Deformation
- Stress-Strain Curves
- Metal/Ductile Materials
- J-Shaped Materials
Shear Stress and Strain
- Shear stress is defined as the force F tangent to a material surface divided by the area A over which the force acts
- Calculated as shear stress = F/A
- Shear strain is the change in angle Δα divided by the original length Lo
- Calculated as shear strain = Δα/Lo
- Shear modulus (G) is the ratio of stress to strain
- G = stress/strain = (F/A) / (Δx/Lo)
Bulk Stress and Strain
- Volume strain measures the change in volume (ΔV) relative to the original volume (Vo) when a substance is subjected to an increase in pressure (ΔP)
- Defined as volume strain = ΔV/Vo
- Bulk modulus (B) quantifies a substance's resistance to compression
- Calculated by B = stress/strain = -ΔP/(ΔV/Vo)
Stress-Strain Curves
- Inelastic/Plastic behavior occurs when an elastic material is stretched/compressed beyond a certain point and does not return to its original state
- The stress beyond which permanent deformation occurs is called the elastic limit
- Some materials, like clay and lead, do not return to their original shapes even after a very small amount of deformation
J-Shaped Stress-Strain Curve
- Curve is characteristic of soft tissue
- This type of tissue behaves elastically for smaller stresses
Liquids and Gases: Pressure
- Pressure is a special type of stress
- You need to know what a fluid is
- Density
- Properties of pressure in a fluid.
States of Matter
- Four states of matter: solid, liquid, gas, and plasma (plasma is not covered)
- Solids
- Molecules oscillate about fixed centers
- Small vibration amplitude; repeated spatial pattern (long-range order)
- Liquids
- Slightly larger intermolecular distances and vibration amplitudes than solids
- Centers are free to move; takes the shape of its container
- Regularity of structure only in the immediate neighborhood (short-range order)
- Gases
- Molecules have much greater kinetic energy, are widely separated and experience very small attractive forces
- The molecules move in straight lines until they collide with another molecule or the container wall
Density
- Density measures mass per unit volume of a solid, liquid, or gas
- Formula: P = m/V, where P is density (kg/m³), m is mass (kg), and V is volume (m³)
Pressure
- Pressure is a special kind of stress that acts in all directions
Atmospheric pressure
- Arises from the force exerted by the motion of atmospheric molecules acting on each square meter of our body
- Approximately 1.013 x 10^5 Pa
- Origin of Pressure:
- Weight of particles above a given level
- Collision of particles with container walls
Properties of Pressure
- Fluid exerts pressure in all directions
- Given depth, pressure is equal in all directions
- Acts perpendicular to the surface in contact with it
- Applied to an enclosed fluid, pressure is transmitted undiminished to all parts of the fluid (Pascal's Principle)
- Can produce a change in volume
- The same at equal depth in a stationary fluid of uniform density, independent of the container's shape
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