4 Materials Flashcards

1
Q

Equation for density

A

p=m/v

Density=mass/volume

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2
Q

Equation for pressure in a fluid (learn)

A

P=hpg

Pressure=height x density x gravity

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3
Q

What is upthrust equal to?

A

The weight of the fluid displaced

U= mg of fluid displaced

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4
Q

Cohesive

A

Forces of neighbouring molecules in the fluid

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5
Q

Adhesive

A

Forces of the surfaces of solids (obstacles/walls of pipe)

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6
Q

Laminar

A

When particles don’t cross over each other (streamlined)

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7
Q

Turbulent

A

When particles do cross over each other

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8
Q

Eddy currents/ vortices

A

When the fluid swirls around and is turbulent

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9
Q

When can Stokes law be used?

A

When a small spherical ball is falling through a fluid in which the flow of the fluid is laminar

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10
Q

Stokes law

A

F=6 x pi x n x r x v

F=viscous drag
n=the coefficient of viscosity
r=radius of sphere
v= velocity

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11
Q

Hookes law

A

k= F/x

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12
Q

Limit of proportionality

A

The point where hookes law ceases to be obeyed

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13
Q

Elastic limit

A

When the load is removed, spring will no longer take original shape

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14
Q

Yield point

A

The onset of plastic flow

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15
Q

Elastic behaviour

A

When a force is exerted the bonds holding the atoms together are stretched

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16
Q

Plastic flow

A

When a force is exerted the layers of atoms slide over each other and can’t return

17
Q

What happens to polymers when a force is applied?

A

Polymers have long chain molecules which are tangled. When a force is applied they untangle and there is a large extension. Then the bond becomes harder to stretch once they are untangled

18
Q

Young’s modulus

A

E=stress/strain

19
Q

Equation for stress

A

Stress= force/area

20
Q

Equation for strain

A

Strain= extension/ original length

21
Q

What is true when stress strain graphs are proportional?

A

The gradient is proportional

22
Q

Strong

A

High breaking stress

23
Q

Hardness

A

How difficult it is to indent the surface

24
Q

Stiffness

A

The gradient of a force extension graph

25
Toughness
The energy density up to fracturing
26
Elastic
Regains original shape when force is removed
27
Ductile
Can be drawn into wires
28
Malleable
Can be hammered into thin sheets
29
Elastic strain energy
Elastic strain energy= force x extension
30
How can elastic strain energy be found on a force extension graph
Area under graph A=1/2Fx A=1/2kx^2
31
What is the gap between the loading and unloading curve in a hysteresis in rubber?
Energy lost as thermal energy
32
Strength
Stress needed to break
33
With reference to the stress strain graph, why are ductile materials suitable for the production of wires
They have a large region of plastic deformation