Chapter 7~ Matter And Materials Flashcards

All key definitions and formulaes (~number represents to the power of that number)

1
Q

What is the definition of density?

A

°Mass per unit volume of a substance

>property of matter
>is constant
>measure of how concentrated the matter is in a particular material
>symbol 'p' - rho
>unit kgm-3 or gcm-3
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2
Q

Formula for density

A

p=m/v

Density =mass /volume

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3
Q

1000kgm-3=

A

1gcm-3

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4
Q

Density of water 💦?

A

1000kgm-3

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5
Q

Pressure is defined as….. ?

A

°As the normal force acting per unit cross- sectional area

> a fluid exerts pressure on walls of its container, or on any surface with which it is in contact
unit : Pa

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6
Q

What produces a high pressure?

A

A big force on a small area

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7
Q

Formula for pressure

A

P=F/A

Pressure =force /area

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8
Q

1 Nm-2=

A

1 Pa

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9
Q

What is a fluid?

A

Liquid or gas

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10
Q

proportional means….

A

° 2 variables that also have a constant ratio between them

If one increases the other will as well…. Also if one decreases so does the other

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11
Q

Atmospheric pressure is due to..?

A

Is the weight of the atmosphere above us, pressing downwards. Pulled by gravity

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12
Q

Pressure in a liquid depends on 3 things

A
  1. Depth (h) below surface
  2. Density (p) of FLUID
  3. The acceleration due to gravity, g
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13
Q

Pressure is proportionate to… :

A

density (p), gravity (g) and depth(h)

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14
Q

Formula for pressure

A

P = pgh

Pressure = density Xacceleration due to acceleration X depth

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15
Q

How to derive p=pgh

🏝️ water in a tank

A
  1. Volume of water = Area X height

V= A X h

  1. Mass of water (m = p X V) = p X A X h
  2. Weight if water (Mg) = p X A X h X g
  3. Pressure = force ÷ area

P= p X A X H x g/A

  1. P = pgh
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16
Q

The 2 forces concerned with changing the shape of a spring…

A
  1. Tensile

2. compressive

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17
Q

Compressive meaning?

A

Describes a force that squeezes an object

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18
Q

Definition of tensile?

A

Associated with tension or a pulling force

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19
Q

Definition of extension

A

The change in length of a material from its original length

20
Q

Hooke’s law :

A

A material obeys Hooke’s law if the extension produced in it is proportional to the applied force (load)

21
Q

Definition of force constant

A

The ratio of force to extention for a spring/wire.

Unit : Nm-1

22
Q

Elastic limit definition

A

The value of stress beyond which an object will not return to its original dimensions.

And from that point on plastic deformation takes place

23
Q

Hooke’s law states that

A

The force applied is proportional to the extention of a material provided Hooke’s limit is not exceeded

24
Q

F=

2 equations

25
Force constant of spring (k) 's unit:
Nm-1
26
Definition of elastic limit
The force beyond which the spring becomes permanently deformed.
27
Definition of strain:
It is defined as the extention per unit length produced by tensile or compressive forces
28
Formula for strain
Strain =extension (x) /original length (l)
29
Stress is defined as...
The force acting per unit cross-sectional area
30
Formula for stress..
Stress =force (F) /cross sectional area (A)
31
Formula for stress..
Stress =force (F) /cross sectional area (A)
32
The 2 units of stress are :
1. Nm-2 2. Pa Nm-2 = Pa
33
Young modulus is defined as
°the ratio of stress to strain for a given material, resulting from tensile forces, provided Hooke's law is obeyed
34
Units for young modulus
Pa
35
Formula for young modulus
=stress /strain Remember : stress =F/A Strain = x/l
36
Young modulus also indicates
The degree of stiffness of a material. The more young modulus, the stiffer it is
37
Stress (y axis) - strain (x axis) graph | Characteristic :
1. Gradient is = to young modulus | Can on use values before or by the elastic limit to get answers.... No values after the elastic limit may be used
38
Definition of elastic potential energy or strain energy :
°energy stored in a stretched or compressed material >the material warms up slightly once stretched or compressed >= work done
39
Force - extention graph characteristics
1. Gradient is = k | 2. Area under the graph is = work done
40
Work done =
1. Force x distance 2. The area under a F-X graph, therefore W or E =1/2 k x~2 0.5 times k times x squared
41
Elastic energy on a F-X graph =
E=1/2 F X Or E= 1/2. K. X~2 0.5 TIMES K TIME X SQUARED
42
Young modulus =
E= STRESS/STRAIN OR E= FL/AX UNIT : Pa
43
Stress - strain graph | The gradient is =
Young modulus
44
3 types of F-X graphs to represent materials are :
Look at notes to get structure of graphs 1. Polymaterial material graph e.g. Rubber, plastic ( hysterisis loop, due to loading and unloading) 2. Brittle material e.g. Glass (constant gradient... Therefore constant k) 3.ductile materials e.g. Wire (constant gradient until Hooke's limit of proportionality)
45
Work done from a F- X graph
E= 1/2KX~2 - 1/2KX~2 UNIT: J
46
3 ways to work out the work done by a spring
1. W=(1/2) k x^2 2. W= (1/2)Fx 3. Area under a F - x graph
47
What is elastic potential energy?
It is the energy stored in a material that is being deformed. Or It is the energy stored in a material due to its tension or compression.