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Edexcel A level Physics > Materials > Flashcards

Materials Flashcards

1
Q

1.

A

B

AKA steepests gradient of straight line part of the graph

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2
Q

Young modulus =

A

Stress/Strain

where E is the Young modulus

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3
Q

young modulus

A

a property of a material that measures how difficult it is to change the shape of a material

unit measured in pascals

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4
Q
A

C

COME BACK TO ADD EXPLANATION

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5
Q

Density =

A
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6
Q

why does frequency of light remains constant during refraction

A

This is a consequence of the principle of conservation of energy. The energy of a wave is directly proportional to its frequency, and since energy cannot be created or destroyed, the frequency of the wave cannot change as it moves from one medium to another.

The frequency of a light wave is determined by the source that generates it.

The frequency of light is directly related to its energy (as described by the Planck-Einstein relation E = hf, where E is energy, h is Planck’s constant, and f is frequency). If the frequency of light were to change upon entering a different medium, it would imply a change in the energy of the photons, which doesn’t happen in such transitions. The conservation of energy principle dictates that the energy (and hence frequency) of the photons remains constant.

COME BACK TO

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7
Q

focal length

A

the distance between the optical centre and the principle focus

The distance from the centre of the lens to the focal point.

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8
Q

Principal focus

A

Principal focus is the point where parallel rays coming from infinity meet or appear to meet.

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9
Q

diverging lens

A

a concave lens

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10
Q

converging lens

A

bulging/convex lens

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11
Q

convex lens

A

converging

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12
Q

concave lens

A

diverging

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13
Q

ray bending in a converging lens

A

going in: bends towards the normal

going out: bends away from the normal

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14
Q

if the object is between the focal length and a converging lens then the image is

A
  • magnified
  • upright
  • virtual image
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15
Q

If the object is beyond the focal length of a converging lens then the image is

A
  • magnified
  • inverted
  • real image
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16
Q

virtual principal focus

A

is you trace back the diverged rays to a single point

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17
Q

power of a diverging lens

A

always negative

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18
Q

What does diverging lens do to the image

A
  • diminished
  • upright
  • virtual image
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19
Q

what does the focal length depend on

A

the curvature of the surface and the material used

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20
Q

the more powerful the lens the

A

shorter the focal length

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21
Q

power of a lens equation

A

P = 1/f

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22
Q

lens equation

A

1/f = 1/u + 1/v
distances to real objects and images are postive
distances to virtual images are negative
focal length of converging is positive, focal length of diverging is negative

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23
Q

magnification equation

A

magnification = image distance/ object distance

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24
Q

real image

A

an image that can be projected onto a screen

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25
Q

virtual image

A

an image that can’t be projected onto a screen (appears to come from behind the lens)

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26
Q

combing lens power

A

P = P1 + P2 + P3…

for thin lenses

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27
Q

Define upthrust

A

Upwards force on an object due to the weight of displaced liquid

Upthrust = weight of fluid displaced

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28
Q

If W > U then,

A

If Weight of an object is greater than Upthrust, object will sink

29
Q

If U < W then,

A

If Weight of an object is greater than Upthrust, object will sink

30
Q

If W < U then,

A

If Upthrust is greater than Weight of an object then the object floats

31
Q

If U > W then

A

If Upthrust is greater than Weight of an object then the object floats

32
Q

What would U-W give us

A

The accelerating force, F

33
Q

What would happen if U=W

A

The object would be stationary
ρW = ρBVg

Vg cancels on both sides because they are the same and then we are left with;

ρW = ρB

34
Q

What is drag?

A

The frictonal force experienced by an object travelling through a fluid (liquid or gas)

35
Q

When an object is moving upwards through a fluid what is the resultant force?

A

Resultant force F = U - (W+D)

where drag is acting downwards

36
Q

When an object is moving upwards through a fluid at constant velocity what is the resultant force?

A

0 = U - (W+D)
U = W+D

where drag is acting downwards

37
Q

When an object is moving downwards through a fluid what is the resultant force?

A

Resultant force F = W - (U+D)

where drag is acting upwards

38
Q

When an object is moving downwards through a fluid at constant velocity what is the resultant force?

A

0 = W - (U+D)
W = U + D

ρWVg = ρBVg + D
ρWVg - ρBVg = D
Vg ( ρW - ρB) = D

39
Q

What is the equation for Weight?

A

W = mg

Weight = mass x gravity

But in fluids (liquids) we often don’t deal with mass we deal with densities so we have;

W = (ρ x V) x g

41
Q

What is upthrust and weight in terms of density?

A

Upthrust is caused by weight of water being displaced.

so,

U = ρW x V x g

where ρW is the density of the fluid

and

W = ρB x V x g

where ρB is the density of the ball in the fluid

The volumes will be the same, because the volume of water displaced will be equal to the volume of ball and of course gravity is the same.

42
Q

When do we use Stokes Law?

A

Whenever we have dynamic viscosity

43
Q

What is Stokes Law?

A

Tells us what the drag force is on a sphere in a fluid

F = F D = 6πηrv

where;
* r is the radius of the sphere
* v is the speed
* η is the dynamic viscosity

44
Q
A

C

increased mass means increased Weight force
smaller diameter means reduced drag force

48
Q

What are tensile forces?

A

Tensile forces produce extension

(in other words trying to stretch an object)

49
Q

What are compressive forces?

A

Reduces the length of a material

(in other words squash an object)

50
Q

What is Hooke’s Law?

A

The applied force is directly proportional to the extension (provided that the limit of proportionality is not exceeded, on a graph this is when it plateaus and we have plastic behaviour)

F = kx

where k is the strength constant or force constant, measured in Nm-1

51
Q

How is extension found?

A

Subtracting final length from the initial length.

52
Q

Define stress

A

(which is similar to pressure, and has same equation)
(tensile or compressive) stress = force/cross-sectional area

53
Q
A

B

Comes from Hooke’s Law; F is y axis and x is x axis. F = Force. x = extension, and we work out extension

Gradient is dF/dx

54
Q

What is the area under a force-extension graph?

A

Elastic potential energy

we know F = kΔx

substituting this in we get

ΔEel = 1/2 k Δx2

55
Q

What is strain?

A

(tensile or compressive) strain = change in length/original length
Calculated by

Strain has no units because its metre/metre so cancels out

which is a percentage of how much object has been stretched

If we have original length one and been stretched by 0.1; we have 0.1/1 = 0.1 which is (10%)

56
Q
A

C

Opposite of elasticity is plasticity and elastic means it goes back to its original shape

58
Q
A

C

W = F x d

59
Q
A

A

Newtons in base units from F = ma

m units are kg
a units are m s-2

so base units of F are kg m s-2

60
Q

Define ultimate tensile strength

A

The greatest amount of stress that a material can withstand before reaching breaking point.

61
Q

Define ductile material

A

A material which can be easily be drawn into wires

65
Q

Define Elastic deformation

A

The material returns to its original shape after the force is removed

66
Q

Define plastic deformation

A

The material does not return to its original shape after the force is removed.

Edexcel A level Physics (1 decks)

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