Topic 4:Materials Flashcards

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1
Q

What is the equation for Density

A

P=M/V

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2
Q

Define turbulent flow

A

where all parts of the fluid cross over into each other and don’t move in a parallel direction.

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3
Q

Define laminar flow

A

Where all the parts of a fluid are flowing in the same direction(parallel direction)

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4
Q

what are the features of Turbulent flow

A

Layers cross over
Produces swirls and eddies
Chaotic movement
Happens at high speeds
Non uniform

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5
Q

What are the features of Laminar flow

A

Parallel Layers
Occurs at lower speeds
Streamline
Velocity is constant over time
uniform

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6
Q

What does turbulent flow cause

A

Drag

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7
Q

What is upthrust equal to

A

Weight of the fluid displaced

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8
Q

Define viscosity

A

The measure of how resistant a fluid is to flowing

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9
Q

What happens to viscosity when heat increases

A

When heat of a liquid increases viscosity decreases

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10
Q

What happens to velocity when viscosity increases

A

The higher the viscosity the more slowly a liquid flows

+viscosity = - velocity

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11
Q

Define drag

A

The forces that oppose the motion of an object moving through a fluid (gas or liquid)

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12
Q

What is the equation for stokes law

A

F=6πrηV

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13
Q

Derive the equation for terminal velocity on a spherical object falling downwards

A

weight =upthrust +Drag

P=M/V so M=P x V

W=MxG
so W=P x V x G
W=Ps x 4/3πr^3 x G

Upthrust= weight of fluid displaced

Weight of fluid displaced = volume of object
V=4/3πr^3
U=4/3πr^3
W=U so
U= Pf x 4/3πr^3 x G

stokes law 6πrηV

W=U+D(stokes law)

Ps x 4/3πr^3 x G = Pf x 4/3πr^3 x G + 6πrηV
(Cancel πr)
(- Pf x 4/3r^2)
then collect like terms
4/3r^2g(Ps–Pf)=6ηV

V=4/3r^2g(Ps–Pf)/6η

V=2/9r^2g(Ps–Pf)/η

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14
Q

Which way does drag act on a falling object

A

upwards

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15
Q

what is the volume of a sphere

A

4/3πr^3

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16
Q

which way does drag act on a rising object

A

downwards

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17
Q

Define Hooke’s law

A

The force applied to a spring is directly proportional to its extension

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18
Q

what is weight equal to as a spherical object falls through a liquid at a terminal velocity an the forces are balanced

A

Weight=upthrust+stokes law

19
Q

What is the equation for Hooke’s law

A

F=KE

20
Q

Define Elastic deformation

A

When an object can compressed/Stretched and returns back to its original shape

21
Q

Define Inelastic deformation

A

When an object can compressed/Stretched but doesn’t return back to its original shape

22
Q

What is the Equation for elastic potential energy

A

EPE=1/2K x X^2

23
Q

How do you find energy from a Force/Extension graph

A

Finding the area under the graph using the equation
1/2 FxE

24
Q

What is the gradient of a force extension graph

A

Spring constant

25
Q

Define spring constant

A

Stiffness(how easy or hard it is to stretch)

26
Q

In a force extension graph define the
Elastic Plastic and fracture stages

A

Elastic= the point where the object will deform and return to its original shape
Plastic= the point where the object will continue deforming with added force, not returning back to its original shape
Fracture=The point where the object breaks

27
Q

Define stress

A

Force per unit of a cross sectional area

28
Q

Define strain

A

Extension per unit length

29
Q

What is the equation for Stress

A

σ=Force/Area

30
Q

What is the equation for Strain

A

ε=Extension/Length

31
Q

What is young modulus

A

The ratio between stress and strain

32
Q

what is the Equation for young modulus

A

Stress/ Strain

Force/area
_____________
Extension/length

Force x length
___________
Area x extension

33
Q

Whats another way to write young modulus

A

Fx/AΔx

34
Q

What is the unit for young modulus

A

Nm^-2

35
Q

What is the gradient of a stress strain graph

A

Young modulus

36
Q

What is the Elastic limit

A

beyond this, the material is permanently deformed & wont return to its original shape

37
Q

What is the limit of proportionality

A

From this region onwards the metal can still behave elastically but cannot be relied upon to do so

38
Q

What is Yield point

A

Beyond this point material undergoes a sudden increase in extension(as the atoms reorganise themselves significantly)

39
Q

What is the Breaking/fracture stress

A

The stress Which causes the material to break.

40
Q

What is the ultimate Tensile Stress

A

The highest value of stress the material can ever attain

41
Q

Define stokes law

A

A way to calculate viscous drag

42
Q

Define viscous drag

A

Viscous drag is The friction between the surface of a object and a fluid as it the object moves through the fluid

43
Q

what is the equation for work done

A

W=force x displacement/distance