Materials Flashcards

1
Q

What is the Density equation?

A
  • Density = mass / volume
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2
Q

What does Upthrust equal?

A

Upthrust = Weight of fluid displaced

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3
Q

What is the Stokes Law equation?

A

F = 6πnrv

F = Force (N)

n = Coefficient of viscosity (Nsm-2)

r = Radius

v = Velocity

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4
Q

When does Stokes Law only apply?

A
  • Only to small spherical objects moving at low speeds with laminar flow or absence of turbulent flow
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5
Q

What happens to the viscosity of most fluids as temp increases?

A
  • Viscosity decreases
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6
Q

What is the Hookes Law equation?

A
  • F = kx
  • F = Force
  • k = Stiffness or Spring constant
  • x = Extension
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7
Q

What is the equation for Stress?

A
  • Stress = Force / Cross sectional area
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8
Q

What is the equation for Strain?

A
  • Strain = Change in length / Original length
  • Strain = No unit
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9
Q

State the graph for a spring.

A
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10
Q

What is the Hookes Law Reigion?

A
  • Where Force is directly proportional to x
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11
Q

What is the limit of proportionality?

A
  • Point where Hookes law ceases to be obeyed
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12
Q

What is the Elastic limit?

A
  • Point beyond which wire will not regain its original length when load is removed.
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13
Q

What is the yield point?

A
  • The onset of plastic flow
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14
Q

What is plastic flow?

A
  • Region where metal deforms extensivly and irreversibly hence plastically. If load is removed there would be little or no change in extension
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15
Q

State the graph for a rubber band.

A

*

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16
Q

What is the equation for Youngs modulus?

A
  • Youngs modulus = Stress / Strain
  • Youngs modulus = Pa
  • Stress = Pa
  • Strain = No unit
17
Q

What is the shape of a stress strain graph?

A
  • Shape is the same as a force extension graph
  • Youngs modulus can be found by the gradient of Hookes law region
  • Ultimate tensile stress (UTS) is the maximum stress a material can bear before it breaks
18
Q

How do you calculate elastic strain energy?

A
  • Eel = 1/2 Fx
  • You can also calculate this via area under force extension graph
  • Area under a stress strain graph is the elastic strain energy per unit volume so to get elastic strain energy you multiply by volume
19
Q

What is Hysterisis in rubber?

A
  • Occurs when rubber band is loaded and unloaded
20
Q

What does a Hysterisis in rubber graph look like?

A
21
Q

What can we find from the Hysteresis graph?

A
  • Elastic strain energy represented by area under loading curve
  • Energy stored in rubber band is represented by area under unloading curve
  • Increase in internal energy within rubber band during one loading and unloading cycle is equal to area enclosed in loop
22
Q

State the difference between compresive and tensile stress?

A
  • Compresive stress shortens an object
  • Tensile stress streches the object
23
Q

What is strength?

A
  • Ability to withstand a large force/high breaking stress before breaking
24
Q

What is stiffness

A
  • Requires large forces for small deformations
25
Q

What is ductile?

A
  • Can be drawn or streched into wires
  • Large plastic deformation before breaking
26
Q

What is elastic

A
  • Regains its original dimensions when a force is removed
27
Q

What is plastic

A
  • Extends extensivly and irreversibly
28
Q

What is toughness?

A
  • Ability to absorb energy from impacts without breaking
29
Q

What is hardness?

A
  • Difficult to indent surface
30
Q

What is malluble?

A
  • Can be hammered into thin sheets
31
Q

What is the opposite of strong?

A
  • Weak
32
Q

What is the opposite to stiff?

A
  • Flexible
33
Q

Opposite to tough?

A
  • Brittle
34
Q

What is the opposite of elastic?

A
  • Plastic
35
Q

What is the opposite of hard?

A
  • Soft
36
Q

What is the opposite to ductile?

A
  • Brittle
37
Q

What is the opposite to malluble?

A
  • Brittle