materials (pmt flashcards)
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Questions and Answers

What is the definition of density for a material?

  • The mass per unit volume. (correct)
  • The weight per unit area.
  • The force per unit volume.
  • The volume per unit mass.
  • Which of these is the correct equation to use to calculate density?

  • Density = Mass * Volume
  • Density = Mass / Volume (correct)
  • Density = Volume / Mass
  • Density = Volume / (Mass * Volume)
  • What is the correct SI unit for density?

  • N/m³
  • kg/m³ (correct)
  • kg/m²
  • g/cm³
  • What does the variable 'A' represent in the stress equation?

    <p>The cross-sectional area</p> Signup and view all the answers

    Which of the following is the correct unit for stress?

    <p>Nm⁻²</p> Signup and view all the answers

    What physical quantity determines the magnitude of the upthrust force an object experiences when submerged in a fluid?

    <p>The weight of the fluid displaced by the object.</p> Signup and view all the answers

    What is the primary factor that determines if an object will float or sink?

    <p>The balance between the object’s weight and the upthrust it experiences.</p> Signup and view all the answers

    In the strain equation, what does ΔL represent?

    <p>The change in length</p> Signup and view all the answers

    Why does a uniform object with a density greater than the liquid it is submerged in always sink?

    <p>Because the object's weight is greater than the upthrust.</p> Signup and view all the answers

    What is the unit used to express strain?

    <p>Unitless</p> Signup and view all the answers

    What does the Young Modulus of a material indicate?

    <p>The relationship between stress and strain, indicating the stiffness of a solid material.</p> Signup and view all the answers

    You have a 2kg block of material which has a volume of 0.1m³. What is the density of the material?

    <p>20 kg/m³</p> Signup and view all the answers

    An object is submerged in water, experiencing an upthrust of 10N. According to the text, this means that the weight of the water that is displaced by the object is approximately:

    <p>Exactly 10 N</p> Signup and view all the answers

    Which formula is used to calculate the Young Modulus?

    <p>$Young Modulus = Stress / Strain$</p> Signup and view all the answers

    What is the standard unit for measuring the Young Modulus?

    <p>Nm⁻²</p> Signup and view all the answers

    In the context of material properties, what is represented by 'L' when calculating strain?

    <p>The original length</p> Signup and view all the answers

    A uniform object submerged in a liquid will sink if:

    <p>Its density is greater than the density of the liquid.</p> Signup and view all the answers

    Stokes' Law is applicable to objects of what shape?

    <p>Spheres</p> Signup and view all the answers

    For Stokes' Law to be valid, what type of flow is required?

    <p>Laminar flow</p> Signup and view all the answers

    What quantity can be calculated using Stokes' Law?

    <p>The viscous drag force on a sphere</p> Signup and view all the answers

    In the Stokes' Law equation $F = 6\pi\eta rv$, what does $r$ represent?

    <p>The radius of the sphere</p> Signup and view all the answers

    What will be the weight of a submerged object relative to the upthrust, if the object's density is greater than that of the liquid?

    <p>The weight will be greater than the upthrust.</p> Signup and view all the answers

    If an object sinks in a fluid, what is the relationship between the density of the fluid and the density of the object?

    <p>The density of the object is greater than the density of the fluid.</p> Signup and view all the answers

    What is the defining characteristic of elastic deformation?

    <p>The object returns to its original shape after the deforming forces are removed.</p> Signup and view all the answers

    When does an object undergo plastic deformation?

    <p>When the object no longer returns to its original shape after the deforming forces are removed.</p> Signup and view all the answers

    According to Hooke's Law, what is the relationship between the extension of an elastic object and the force applied?

    <p>The extension is directly proportional to the force applied, up to its limit of proportionality.</p> Signup and view all the answers

    What is the significance of the limit of proportionality?

    <p>It is the point after which Hooke's Law is no longer applicable.</p> Signup and view all the answers

    What is the elastic limit of a material?

    <p>The point at which an object stretches beyond recovery.</p> Signup and view all the answers

    What mathematical equation represents Hooke's Law?

    <p>$F = k\Delta x$</p> Signup and view all the answers

    How is mechanical stress defined?

    <p>The force experienced by the object per unit area.</p> Signup and view all the answers

    Which of the following is true for an object that has been deformed past its elastic limit?

    <p>It will have undergone permanent plastic deformation.</p> Signup and view all the answers

    What is breaking stress?

    <p>The maximum stress that an object can withstand before fracturing</p> Signup and view all the answers

    What does the yield point signify in materials?

    <p>The point beyond which an object experiences large extension without substantial force increase</p> Signup and view all the answers

    What type of energy is stored in a stretched object?

    <p>Elastic Potential Energy</p> Signup and view all the answers

    Which of the following equations represents the energy stored in a spring?

    <p>E = ½ kΔx²</p> Signup and view all the answers

    In a force-extension graph, what does the gradient represent?

    <p>The elastic constant (k)</p> Signup and view all the answers

    What does the area under the curve on a force-extension graph represent?

    <p>The elastic potential energy stored in the spring</p> Signup and view all the answers

    What does the gradient represent on a stress-strain graph?

    <p>The Young Modulus of the material</p> Signup and view all the answers

    Which equation calculates the energy stored in a spring in terms of force and displacement?

    <p>E = ½ FΔx</p> Signup and view all the answers

    Signup and view all the answers

    Study Notes

    Density

    • Density is defined as mass per unit volume
    • The equation for density is: Density = Mass/Volume
    • The unit of density is kg/m³

    Upthrust

    • Upthrust is equal to the weight of the fluid displaced by a submerged object.

    Floating and Sinking

    • An object floats if the upthrust is greater than or equal to the weight of the object.
    • An object sinks if the weight of the object is greater than the upthrust.

    Stokes' Law

    • Stokes' Law applies to small spherical objects in a fluid with laminar flow.
    • The equation for Stokes' Law is: F = 6πηrv
      • η is the viscosity of the fluid
      • r is the radius of the sphere
      • v is the speed of the sphere

    Elastic Deformation

    • Elastic deformation occurs when an object returns to its original shape after the deforming forces are removed.

    Plastic Deformation

    • Plastic deformation occurs when an object does not return to its original shape after the deforming forces are removed. It will have permanent deformation.

    Hooke's Law

    • Hooke's Law states that the extension of an elastic object is directly proportional to the force applied to it, up to its limit of proportionality.
    • The equation for Hooke's Law is: F = k∆x
      • F is the force applied (N)
      • k is the stiffness constant
      • ∆x is the extension (m)

    Limit of Proportionality

    • The limit of proportionality is the point beyond which the force and extension are no longer directly proportional to each other. Hooke's law is no longer obeyed.

    Elastic Limit

    • The elastic limit is the point beyond which an object will no longer elastically deform and will instead deform plastically.

    Mechanical Stress

    • Mechanical stress is the force experienced by an object per unit area.
    • The equation for stress is: Stress = F/A
      • F is the force applied
      • A is the cross-sectional area
    • The unit of stress is Nm⁻²

    Strain

    • Strain is a unitless quantity because it's the ratio of two lengths.
    • The equation for strain is: Strain = ∆L/L
      • ∆L is the change in length
      • L is the original length

    Young Modulus

    • A material's Young Modulus is a measure of how much force is required for a given extension, regardless of the object's dimensions.
    • The equation for Young Modulus is Stress/Strain
    • The unit of Young Modulus is Nm⁻².

    Breaking Stress

    • Breaking stress is the maximum stress that an object can withstand before fracturing.

    Yield Point

    • The yield point is the point beyond which an object will experience a large extension without a substantial increase in the force applied.

    Elastic Potential Energy

    • Elastic potential energy is the type of energy stored in an object that has been stretched.

    Energy Stored in a Spring

    • The equations for energy stored in a spring are:
      • E = ½F∆x
      • E = ½k∆x²

    Force-Extension Graph

    • The gradient of the linear region represents the elastic constant (k).
    • The area under the linear region is equal to the elastic potential energy stored in the spring.

    Stress-Strain Graph

    • The gradient of the linear region represents the Young Modulus of the material.

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    Description

    This quiz explores key concepts in physics related to density, upthrust, floating and sinking, and deformation. It covers Stokes' Law and the differences between elastic and plastic deformation. Test your understanding of these fundamental principles.

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