Materials Flashcards

(35 cards)

1
Q

What is Archimedes’ principle

A
  • Upthrust magnitude=weight of fluid displaced by the body
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2
Q

What is upthrust

A
  • When a body is fully or partially submerged in a fluid, pressure differences at different depths cause it to experience an upward force- upthrust
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3
Q

What is laminar flow

A
  • Flow in layers
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4
Q

Characteristics of laminar flow

A
  • Occurs at lower speeds and around streamlined objects
  • Layers do not mix and are roughly parallel to each other
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5
Q

What happens in turbulent flow

A
  • Flow is chaotic and subject to sudden change in speed and direction
  • Large scale mixing of fluid layers
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6
Q

What are streamlines

A
  • Lines of laminar flow
  • At any point in each of these streamlines the velocity with time of the flow will be constant
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7
Q

What is viscous drag on objects

A
  • The frictional force between layers of fluid being present when a solid moves through a liquid
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8
Q

When is viscous drag largest

A
  • In turbulent flow rather than laminar flow
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9
Q

What does stokes law equation give us

A
  • Formula for viscous drag for small spheres at low speeds in laminar flow
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10
Q

What is Hooke’s law

A

The force needed to extend a spring is proportional to the extension of the spring

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11
Q

When is Hooke’s law obeyed

A
  • If material has not passed its limit of proportionality
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12
Q

What is Hooke’s law equation

A

Force=stiffness x extension

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13
Q

What is distortion

A
  • A change in shape of an object
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14
Q

What is elastic distortion

A
  • Temporary distortion- will go back to its original shape
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15
Q

What is inelastic/plastic distortion

A
  • permanent distortion- will not go back to original shape
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16
Q

What is the elastic limit

A
  • The maximum force a body can endure and still regain original shape and size
17
Q

What is the limit of proportionality

A

The point where Hooke’s law ceases to be obeyed

18
Q

What is elasticity

A
  • The property a material has whereby it regains its original size and shape when a deforming force is removed
19
Q

What is stiffness

A
  • A measure of a body’s resistance to changes in size/shape
20
Q

What is a yield point

A
  • When a large extension is produced for a very small increase in force
  • The material of the body is said to show ‘plastic’ behaviour
21
Q

When do stress and strain occur

A

When forces deform an object it is said to be STRESSED. As a result the material becomes STRAINED

22
Q

What is stress

A
  • The force per unit area acting on a material
23
Q

What is strain

A

The extension per unit original length

24
Q

What is young modulus

A

The measure of the ability of a material to withstand changes in length with an added load

25
What is the ultimate tensile stress/ultimate strength
Th highest value of stress attained in the material
26
What is the fracture/breaking stress
The value of stress in the material when the sample breaks
27
What is the area under the graph of a stress/strain graph equal to
Energy stored per unit volume
28
What is strength
- A measurement of how much a material resists stress/deformation - A strong material has a high breaking stress
29
What is ductility
- A property that allows materials to be drawn into a wire, because it can be pulled without breaking due to layers of atoms able to slide over each other
30
What is malleability
- A property that allows a material to be hammered/pressed into shape when it experiences compressive stress - Atoms in layers and can slide over each other
31
What is creep
A permanent deformation that increases slowly with time due to constant mechanical stress
32
How to identify stiff object
- Steep gradient on force extension graph - High young modulus
33
What is toughness
- High energy density up to a fracture
34
What is hardness
- Difficult to indent the surface
35
What is elastic strain energy
- The energy stored in the material due to the work being done on the material in stretching it